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The ACES2 Namelist Job Control Parameters

The job control parameters in the ACES2 namelist define the currently available options. These options are set through the use of keywords.

Within the keyword framework, each parameter may be specified by either an integer or a specific name, unless the parameter corresponds to a number. In this case, of course, both forms are equivalent. All possible keywords in the ACES2 namelist are discussed below:

Specifies the way that the $\langle ab\vert\vert cd\rangle$ molecular orbital integrals are handled in post-MBPT(2) calculations. STANDARD (= 0) uses a technique which results in a minimum amount of CPU time but a maximum usage of disk space (particularly during execution of program XINTPRC); MULTIPASS (= 1) reduces the amount of disk storage required during XINTPRC, but at the cost of additional CPU time; AOBASIS (= 2) uses an AO-based algorithm to evaluate all terms involving these integrals. Again, use of this option results in larger CPU times (particularly on vector supercomputers), but reduces the amount of required disk storage significantly. The use of ABCDTYPE=AOBASIS, however, is strongly recommended for CC calculations on work station computers. It might be however noted that the option ABCDTYPE=AOBASIS is not available for all type of calculations. (Default: STANDARD).

Specifies treatment of anharmonc effects by calculating cubic and/or quartic force fields. ANHARM=VIBROT requests calculation of the cubic force field needed for the determination of vibration-rotation interaction constants, while ANHARM=QUARTIC requests in addition calculation of parts of the quartic force fields required for the determination of anharmonic effects on vibrational frequencies. Default: NO).

Specifies which algorithm is used for ANHARM=VIBROT and QUARTIC calculations. If STANDARD (= 0), then simply invoking xaces2 will cause the complete job to be run, with all second derivative calculations being done in series. If PARALLEL (= 1), then the job stops after the second derivative calculation at the reference geometry and prints out input files for all required points. These can then be run separately with the output processed by the procedure described elsewhere in this manual. Please do not use PARALLEL unless you are a real expert.

Controls the stepsize used in anharmonic force field calculations. The value is specified in reduced normal coordinates, which are dimensionless. The actual stepsize used in the calculation is 10$^6$ the value specified (as an integer) in the ZMAT file. (Default: 150000).

Specifies whether nonabelian symmetry is to be exploited in determining displacements for ANHARM=VIBROT or QUARTIC calculations. If set to NONABELIAN (= 0), maximum advantage will be taken of symmetry and the full set of cubic force constants will be generated from a skeleton set by application of the totally symmetric projection operator. If set to ABELIAN (= 1), only the operations of the abelian subgroup will be exploited. It is important to point out that the symmetrization currently works only for cubic constants. Therefore, if you require quartic force constants (for frequency calculations), you MUST use the ABELIAN option. Moreover, the latter work for only asymmetric tops and linear molecules.

Can be used to control the algorithm used by ACES2 when terms involving $\langle ab\vert\vert cd\rangle$ molecular orbital integrals are calculated in the atomic orbital basis (see keyword ABCDTYPE above). MULTIPASS (= 0) uses an approach where the AO integral file is read a number of times in order to ensure maximal vectorization and is usually the optimal strategy on supercomputers; SINGLEPASS (= 1) determines the contributions with only a single pass through the AO integrals, but at the cost of significantly reduced vectorization. In general, however, SINGLEPASS is definitely preferable on workstations with RISC architectures. (Default : MULTIPASS on all 64-bit machines (e.g., CRAY-YMP) ; SINGLEPASS on all 32-bit machines (e.g., IBM-RS6000, HP-735, SGI-Indigo, DEC alphastations)).

Specifies the name of the basis set for all atoms in the system under study. Accepted values are: STO-3G, DZ, 3-21G, 4-31G, 6-31G, 6-311G, DZP, TZP, TZ2P, 6-31G*, 6-31G**, 6-311G*, 6-311G**, PVDZ, PVTZ, PVQZ, PV5Z, PBS and WMR. basis sets. For hydrogen atoms, the Pople `` *" and `` **" basis sets default to the corresponding basis with no polarization functions and $p$ functions, respectively. In order for this to work, the appropriate basis sets must be in the GENBAS file for all atoms. If you want to use different basis sets on different atoms, to use ghost atoms, or to use a basis which is not in the above list (there are several such families in the standard GENBAS file), the section entitled `` Non-Standard Basis Set Specification" should be consulted. Non-standard basis set specification involves setting the BASIS keyword to SPECIAL (equivalently, it may be set to 0 or omitted). A complete list of the basis sets currently in the standard GENBAS file in given in section B of Part IV of this manual. (Default: SPECIAL)

This option specifies the convergence criterion in Brueckner-based coupled-cluster or configuration interaction calculations. The calculation is considered converged when the large single excitation amplitude falls below 10$^{-N}$, where $N$ is the value associated with the keyword. (Default : 4)

Specifies whether Brueckner orbitals are to be determined for the specified CC method. OFF (= 0) Brueckner orbitals are not to be determined, ON (= 1) They are to be determined. (Default : 0).

The number of records held in the i/o cache used by the post-SCF programs. The maximum number of records which can be held is 100. (Default : 10)

Defines the level of calculation to be performed. =0 SCF; =1 MBPT[2]; =2 MBPT[3]; =3 SDQ-MBPT[4]; =4 MBPT[4]; =5 LCCD; =6 LCCSD; =7 UCCSD[4]; =8 CCD; =9 UCC[4]; =10 CCSD; =11 CCSD + T[CCSD]; =13 CCSDT-1; =14 CCSDT-1b; =15 CCSDT-2; =16 CCSDT-3; =17 CCSDT-4; =18 CCSDT; =21 QCISD[T]; =22 CCSD[T]; =23 QCISD; =24 CID; =25 CISD; =31 CC2; =32 CC3. (Default : SCF).

The convergence criterion for the CC equations. Equations are considered converged when the maximum change in amplitudes is less than $10^{-N}$. (Default : N=7).

Maximum number of expansion vectors used in the iterative subspace to enhance convergence in the solution of the CC equations. (Default : 5).

Specifies the type of convergence acceleration used to solve the CC equations. RLE (= 0), the RLE method of Bartlett and Purvis is used with periodic extrapolation of the solution vector; DIIS (= 1) uses the DIIS approach of Pulay; NOJACOBI (= 2) uses the RLE method with continuous extrapolation; OFF (= 3) no convergence acceleration method is used. In general, DIIS provides the best performance and is therefore the default. Use of OFF is generally a bad idea for CC calculations, but may be preferable to the other choices for configuration interaction calculations. Note that the DIIS procedure of Pulay is the default and the only available method for solving perturbed CC and $\Lambda$ equations. (Default : DIIS).

The maximum number of CC iterations. (Default : 50).

Specifies which CC program is used. The available modules are VCC(=0), ECC(=1), and EXTERNAL(=2). The default is for all calculations VCC, as ECC is currently a more experimental code. EXTERNAL stands for interfaces to CC programs outside the usual ACESII sequence, e.g., the general CC module by Mihaly Kallay.

The molecular charge. (Default : 0).

Convergence threshold for CIS calculations. (Default: 5)

The contraction scheme used by the integral and integral derivative programs. SEGMENTED (= 0) uses a segmented contraction scheme; GENERAL (= 1) uses a general contraction scheme. NOTE: Even for truly segmented basis sets, both programs run significantly faster in GENERAL mode, and this should be used in practice. (Default: GENERAL).

Specifies convergence criterion for geometry optimization. Job terminates when RMS gradient is below $10^{-N}$ Hartree/bohr, where $N$ is the value specified by CONVERGENCE. (Default: 4; Value must be specified as an integer).

The keyword INTERNAL(=0) means that the geometry is supplied in the usual Z-matrix format, while CARTESIAN(=1) means that the geometry is given in cartesian coordinates. A third option XYZ2INT(=2) is available, in which a Z-matrix connectivity is defined, but with values of the internal coordinates defined implicitly by supplied Cartesian coordinates. An example of this type of input is included later in the manual. Note that geometry optimizations are possible only when internal coordinates have been defined, i.e. only for COORDINATES=INTERNAL or COORDINATES=XYZ2INT. (Default : INTERNAL)

Specifies the convergence criterion for the iterative solution of the CPHF and Z-vector equations. The solutions are considered to be converged when the residual norm of the error vector falls below 10$^{-N}$. (Default : 12)

The maximum number of cycles allowed for the solution of the CPHF and Z-vector equations. (Default : 64)

Specifies whether or not Hessian matrix is transformed (nonlinearly) to curvilinear internal coordinates. A value of 0 (or OFF) turns the transformation off if the analytic force constants are not available, while it is always performed if CURVILINEAR=1 (or ON). Values higher than 1 (or NO) unconditionally turn the transformation off.(Default: ON if analytic Hessian is available, OFF otherwise).

Specifies whether or not derivatives of the energy are to be calculated and if so whether first or second. = 0 Derivatives not calculated, =1 First derivatives to be calculated, =2 Second derivatives to be calculated. This need not be set in geometry optimization or vibrational frequency calculations since it is automatically set if the appropriate options in the ACES2 namelist are set. (Default : 0). NOTE: It may be dangerous to use this keyword.

Specifies whether orbital relaxed (RELAXED =0) or orbital unrelaxed (UNRELAXED =1) derivatives are calculated in a CC calculation. (Default : RELAXED)

Specifies which molecular orbitals will be dropped from the post-SCF calculation. The orbitals are numbered in ascending order from the most stable (negative energy) to the most unstable (largest positive energy). Individual orbitals must be separated with a dash, while x$>$y means orbitals x through y inclusive. For example, the string 1$>$10-55-58$>$64, would result in orbitals 1,2,3,4,5,6,7,8,9,10,55,58,59,60,61,62,63 and 64 being dropped. For UHF calculations, the appropriate orbitals are deleted for both spin cases. No dropped MOs are currently allowed for gradient or property calculations. (Default : No dropped MOs)

This specifies whether effective core potentials (some kind of pseudopotentials) are used (ON = 1) or not (OFF = 0). (Default : OFF)

Specifies which eigenvector of the totally symmetric part of the block-factored Hessian is to be followed uphill in a transition state search. Eigenvectors are indexed by their eigenvalues - the lowest eigenvalue is 1, the next lowest is 2, etc. The default is 1, which should always be used if you are not looking for a specific transition state which you know corresponds to motion along a different mode. In the future, relatively sophisticated generation of a guessed eigenvector will be implemented, but this is the way things are for now. Of course, the value of EIGENVECTOR has no meaning if METHOD is not set to TS. (Default: 1; Value must be specified as an integer).

Controls whether non-iterative triples corrections are applied after various types of EOM-CCSD calculation. Works with EOMIP, might work with EOMEE, certainly doesn't work with EOMEA. Use with great caution, preferably after having a few drinks. Options are OFF and ON. (Default : OFF)

Tells ACES II to recompute the Hessian every N cycles, where N is the supplied argument. For correlated calculations, the Hessian is evaluated only at the SCF level. (Default: 0 (no recomputation); Value must be specified as an integer).

The maximum number of expansion vectors used in the solution of EOMCC equations (Default : 20)

This keyword applies only to EOM-CC calculations and specifies whether any excited or ionized state one-electron properties are to be calculated. Proper use of this keyword requires a relatively advanced knowledge of quantum chemistry and the available options are discussed here. The options are : OFF (=0) [no properties or transition moments are calculated]; EXPECTATION (=1) [transition moments and dipole strengths are calculated along with selected one-electron properties which are evaluated as expectation values]; UNRELAXED (=2) [selected one-electron properties are calculated in an approximation that neglects relaxation of molecular orbitals]; RESPONSE (=3) [selected one-electron properties are calculated as analytic first derivatives of the energy]. Except for EOMCC calculations on two-electron systems (which are exact), properties obtained by the three approaches will not be equivalent. The default value for this keyword is slightly complicated. For TDA calculations, the default is EXPECTATION since the evaluation of transition moments involves only a negligible amount of additional computation relative to the evaluation of the excitation energies. For EOMCC, the default is OFF since evaluation of any transition moments or properties requires approximately twice the computational time. Transition moments and dipole strengths are evaluated by default for all values of ESTATE_PROP other than OFF.

This specifies the number of excited states which are to be determined in each irreducible representation of the computational subgroup. The program attempts to find all of the lowest roots, but this is not guaranteed because the eigenvalue problem is not solved by direct matrix diagonalization, but rather by an iterative (modified Davidson) algorithm. For excited state gradient calculations, only one root can be specified, so only one non-zero entry in the string is allowed, and that must be set to one. The format used for this keyword is identical to that used in the OCCUPATION keyword. For example, for a computational subgroup having four symmetry species, the string ESTATE_SYM=3/1/0/2 specifies that 6 total roots should be searched for, three in the first block, one in the second block, and two in the fourth block. (Default : All zeros).

The tolerance used in converging EOM-CC excited state calculations. By default, the iterative diagonalization continues until the RMS residual falls below $10^{-5}$, but this value can be changed to $10^{-N}$ by specifying ESTATE_TOL=N. (Default : 5)

This keyword specifies the type of excitation energy calculation which is to be performed. Available options are NONE (=0); TDA (=1) [the Tamm-Dancoff, or configuration interaction singles (CIS) approach]; EOMEE (=3) [the equation of motion coupled-cluster approach for excited states]; EOMIP (=4) [the equation of motion coupled-cluster approach for ionized states; CIS (=5) [equivalent to TDA]; CIS[D] (=6) [the CIS(D) method]. Calculations at the EOMIP-CCSD(2) and EOMEE-CCSD(2) level can be run by combining the EOMIP or EOMEE options with CALC_LEVEL=MBPT[2]. EOMEE calculations are currently available for CCSD, CCSDT-1, CCSDT-1b, CCSDT-2, CCSDT-3 and CC3, although all but CCSD should be run only by experts and those who very carefully monitor program output. (Default : NONE).

Specifies the strength of a Fermi-Contact pertubation as required for finite-field calculations of spin densities and the FC contributions to indirect spin-spin coupling constants. The value must be specified as an integer and the FC strength used by the program will be the value of the keyword $x 10^{-6}$. The atom for which the FC perturbation is switched on is specified in the ZMAT file after the ACES2 command line and potential basis set input, as follows
%spin density
with N as the number of atom (in (X5,I3) format) in the order they are written by JODA to the MOL file. Be aware that for some atoms, the calculation has to be run in lower symmetry or even without symmetry. (Default : 0)

In finite difference calculations using the FINDIF option, this keyword controls the algorithm used to compute the harmonic force constants. GRADONLY (= 0) evaluates the force constants and dipole moment derivatives by numerical differentiation of analytic gradients; ENERONLY (= 1) evaluate the force constants by second differences of energies (dipole moment derivatives are not evaluated); while MIXED (= 2) evaluates $1 x 1$ blocks of the symmetry-blocked force constant matrix by second differences of energies and all other elements by first differences of gradients. The GRADONLY and MIXED approaches may, of course, only be used when using computational methods for which analytic gradients are available.

In finite difference calculations using the FINDIF option, this keyword controls whether or not rotational degrees of freedom are projected out of symmetry-adapted coordinates. ON (= 0) uses rotationally projected coordinates, while OFF (= 1) retains the rotational degrees of freedom. At a stationary point on the potential surface, both options will give equivalent harmonic force fields, but OFF should be used at non-stationary points. (Default : ON)

This keyword may be used to request that only vibrational frequencies of certain symmetry types be evaluated in a VIBRATION=FINDIF calculation. The numbers of the irreducible representations for which vibrational analysis is to be performed are separated by slashes. For example, FD_IRREP=1/3/4 means compute the frequencies of modes transforming as the first, third, and fourth irreducible representations. If a symmetry is specified for which there are no vibrational modes, the program will terminate. The labels of the irreducible representations for this keyword are not usually the same as those used in the rest of the calculation. Moreover, for some point groups, for example those of linear molecules, the two sets of labels refer to different subgroups. There is as yet no straightforward way to determine what they will be without starting a calculation. If one runs the xjoda and then the xsymcor executables the relevant irreducible representations will be listed. If all vibrational frequencies are desired, this keyword need not be included. (Default : compute vibrational frequencies for all irreducible representations)

Specifies step length (in $10^{-4}$ amu$^{1/2}$ bohr) used in generating the force constant matrix by finite difference of Cartesian gradients. (Default: 50 (0.005 amu$^{1/2}$ bohr)).

In finite difference calculations using the FINDIF option, this keyword specifies the point group to be used in generating the symmetry-adapted vibrational coordinates. FULL (= 0) specifies the full molecular point group, COMP (= 1) specifies the Abelian subgroup used in the electronic structure calculation. (Default : FULL)

This specifies the physical length (in integer words) of the records used in the word-addressable direct access files used by ACES II. This value should always be chosen as a multiple of 512 bytes, as your local system manager certainly understands. (Default : 2048).

This option allows the splitting of files. Input is required in the form FILE_STRIPE=N1/N2/N43/N4/N5, where N1, N2, N3, N4, and N5 specify the number of files in which MOINTS, GAMLAM, MOABCD, DERINT, and DERGAM are splitted, respectively. (Default : 0/0/0/0/0)

This option allows addition of arbitrary perturbations to the one-electron Hamiltonian. Those are turned on by non-zero values for the keyword, the corresponding field strength is N*$x 10^{-6}$. The type of requested perturbation is specified in the ZMAT file as follows
label   num
the label corresponds to the character string used by the module xvprops, i.e. ' X ' for dipole integrals in x direction, ' QXX ' for quadrupole integrals, or ' FZZ ' for electric field integrals. The number of the connected atom (for example, in case of electric field integrals) has to be given in I3 format if required. (Default : 0).

This option is used to control the algorithm used for construction of the Fock matrix in SCF calculations. PK (= 0) uses the PK-supermatrix approach while AO (= 1) constructs the matrix directly from the basis function integrals. In general, PK is somewhat faster, but results in considerable use of disk space when out-of-core algorithms are required. (Default : FOCK).

Used to control the handling and storage of two-particle density matrix elements with four virtual indices $\Gamma(abcd)$. DISK (=0) directs the program to calculate and store all elements of $\Gamma(abcd)$, while DIRECT (=1) tells the program to use alternative algorithms in which $\Gamma(abcd)$ is calculated and used ``on the fly''. Note that this option might be not available for all type of calculations. (Default : DISK).


This keyword applies only to Hydrogen and Helium atoms and specifies the number of contracted Gaussian functions per shell. There is usually no need to use this keyword, but it can be useful for using a subset of the functions in a particular entry in the GENBAS file, particularly for generally contracted basis sets. For example, if entry H:BASIS in the GENBAS file contains 7 contracted $s$ functions, 4 $p$ functions and a single $d$ function, then setting GENBAS_1=730 would eliminate the last $p$ function and the $d$ function. The default for this keyword is to use the unaltered GENBAS entry.

This keyword performs the same function as GENBAS_1 above, but applies only to second-row atoms.

This keyword performs the same function as GENBAS_1 and GENBAS_2, but applies only to third-row atoms.

Keyword used to control type of grid calculation (see later section in this manual). Options are OFF (= 0), no grid calculation; CARTESIAN (= 1), steps are in Cartesian coordinates (which must be run with COORD=CARTESIAN); INTERNAL (= 2), steps are in Z-matrix internal coordinates; QUADRATURE (= 3) steps are chosen for an integration based on Gauss-Hermite quadrature. (Default : OFF)

Where the initial SCF eigenvectors are read from. MOREAD means to read from the disk (the `` JOBARC" file) and CORE means to use a core Hamiltonian initial guess. If MOREAD is chosen but no disk file is present, the core Hamiltonian is used. (Default : MOREAD)

This keyword determines which action is taken by the linear response program. ON (= 1) the full effective Hamiltonian is calculated and written to disk; OFF (= 0) the ``lambda'' linear response equations are solved. (Default : 0)

This is used to control checks of the stability of RHF, ROHF and UHF wavefunctions, as well as a cursory search for a lower SCF solution (but probably doesn't work for ROHF although it could be implemented by an interested Daniel). There are three possible options for this keyword. OFF (=0) does nothing, while ON (=1) performs a stability check and returns the number of negative eigenvalues in the orbital rotation Hessian. A third option, FOLLOW (=2) performs the stability check and then proceeds to rotate the SCF orbitals in the direction of a particular negative eigenvalue of the orbital rotation Hessian (see the explanation of keyword ROT_EVEC), after which the SCF is rerun. A more detailed discussion of HF stability testing may be found in the section entitled Hartree-Fock Wavefunction Stability Analysis, below. (Default : OFF)

This keyword can be used to significantly reduce disk i/o, and should be implemented very soon. The following options are available: OFF (= 0), no special algorithms are used (the default case); ALL (=1) all quantities except the $\langle ab\vert\vert cd\rangle$ molecular integral lists are held in core; PARTIAL (= 2), the T2 and T1 vectors are held in core throughout the calculation; (=4) all quantities except the $\langle ab\vert\vert cd\rangle$ and $\langle ab\vert\vert ci\rangle$ integrals are held in core; (=5) $\langle ij\vert\vert kl\rangle$ and $\langle ij\vert\vert ka\rangle$ and two-index quantities are held in core; (=6) all direct access files (MOINTS, GAMLAM, etc.) are held in core. At present, these options have been implemented only in the energy code (xvcc) and the excitation energy code (xvee). (Default : 0)

This keyword defines what type of integral input will be written by JODA. VMOL (=1) has to be used with the programs of ACES II. Using ARGOS (=0) input for Pitzer's ARGOS integral program will be written. (Default : VMOL).

Controls amount of debug printing performed by Joda. The higher the number, the more information is printed. Values of 25 or higher generally do not produce anything of interest to the general user. Do not set JODA_PRINT to 999 as this will cause the core vector to be dumped to disk. (Default: 0; Value must be specified as an integer).

The tolerance for basis set linear dependence. =N The basis set is considered linearly dependent and eigenvectors of the overlap matrix are neglected if the associated eigenvalues are less than $10^{-N}$. (Default: 8).

Convergence threshold for linear equations controlled by LINEQ_TYPE. Equations are iterated until smallest residual falls below $10^{-N}$, where N is the value associated with this keyword (Default: 7).

Determines the algorithm used to solve linear equations ($\Lambda$ and derivative $T$ and $\Lambda$). POPLE (=0) uses Pople's method of successively orthogonalized basis vectors, while DIIS (=1) uses Pulay's DIIS method. The latter offers the practical advantage of requiring much less disk space, although it is not guaranteed to converge. Moreover, POPLE has not been tested for some time and should definitely be checked! (Default : DIIS)

Maximum subspace dimension for linear equation solutions. (Default: 0, which is rather curious) EVIDENTLY, HOWEVER, THIS KEYWORD DOES NOT ACTUALLY WORK AND THIS PARAMETER IS CONTROLLED BY CC_EXPORDER!

The maximum number of iterations in all linear CC equations. (Default : 50)

This keyword is used by the SCF program to determine if the orbital occupancy (by symmetry block) is allowed to change in the course of the calculation. ON (= 1) locks the occupation to that set by the keyword OCCUPATION [or the initial guess if OCCUPATION is omitted]; OFF (= 0) permits the occupation to change. (Default : 1 if the occupation is specified with the OCCUPATION keyword and in second and later steps of optimizations ; 0 if OCCUPATION is omitted.)

Specifies largest step (in millibohr) which is allowed in geometry optimizations. (Default: 300).

Specifies the total core memory used, in units of integer words. (Default : 6 500 000).

Specifies the geometry optimization strategy. Four values are permitted: 0 (or NR) -- Straightforward Newton-Raphson search for minimum; 1 (or RFA) -- Rational Function Approximation search for minimum (this method can be used to find minima when the initial structure is in a region where the Hessian index is nonzero); 2 (or TS) Cerjan-Miller eigenvector following search for a transition state (can be started in a region where the Hessian index is not equal to unity); 3 (or MANR) -- Morse-adjusted Newton-Raphson search for minimum (very efficient minimization scheme, particularly if the Hessian is available); 4 is currently unavailable; 5 (or SINGLE_POINT) is a single point calculation. (Default: SINGLE_POINT).

The spin multiplicity. (Default : 1 )

Tells the program what to do if negative eigenvalues are encountered in the totally symmetric Hessian during an NR or MANR search. If NEGEVAL=0 (or ABORT), then the job will terminate with an error message; if NEGEVAL=1 (or SWITCH) the program will just switch the eigenvalue to its absolute value and keep plugging away (this is strongly discouraged); and if NEGEVAL=2 (or$\rightarrow$RFA), METHOD is switched to RFA internally and the optimization is continued. (Default: ABORT).

This flag tells the correlation energy code if the reference function satisfies the Hartree-Fock equations. Usually there is no need to set this parameter, since standard non-HF reference functions (QRHF and ROHF) set this flag internally. However, if you are inputting a set of orbitals to the correlation energy code directly, it may be necessary to use NON-HF. ON (= 1) signifies that a non-HF reference function is used; OFF (= 0) is used for HF reference functions. (Default : 0).

Specifies how many t amplitudes will be printed for each spin case and excitation level. =N The largest N amplitudes for each spin case and excitation level will be printed. (Default : 15).

Specifies the orbital occupancy of the reference function in terms of the occupation numbers of the orbitals and their irreducible representations. The occupancy is specified by either NIRREP or 2*NIRREP integers specifying the number of occupied orbitals of each symmetry type, where NIRREP is the number of irreducible representations in the computational point group. If there are no orbitals of a particular symmetry type a zero must be entered. If the reference function is for an open-shell system, two strings of NIRREP occupation numbers separated by a slash (`/ ') are input for the $\alpha$ and $\beta$ sets of orbitals. An example of the use of the OCCUPATION keyword for the water molecule would be OCCUPATION=3-1-1-0. For the $^2$A$_1$ water cation, an open-shell system, the keyword would be specified by OCCUPATION=3-1-1-0/2-1-1-0. It should be noted that the VMOL integral program orders the irreducible representations in a strange way which most users do not perceive to be a logical order. Hence, it is usually advisable initially to run just a single point integral and SCF calculation in order to determine the number and ordering of the irreducible representations. The occupation keyword may be omitted, in which case an initial orbital occupancy is determined by diagonalization of the core Hamiltonian. In many cases, SCF calculations run with the core Hamiltonian guess will usually converge to the lowest energy SCF solution, but this should not be blindly assumed. (Default : The occupation is given by the core Hamiltonian initial guess).

specifies which kind of open-shell CC treatment is employed. The default is a spin-orbital CC treatment (SPIN-ORBITAL=1) which is the only possible choice for UHF-CC schemes anyways. For ROHF-CC treatments, the possible options are beside the standard spin-orbital scheme a spin-restricted CC approach (SR-CC=3), as well as a corresponding linear approximation (which in the literature usually is referred to as partially-spin-adapted CC scheme) (PSA-CC=1). SR-CC and PSA-CC are within the CCSD approximation restricted to excitations defined by the first-order interacting space arguments. Full inclusion of all double excitations can be achieved by using SR-CC_FULL (=4) and PSA-CC_FULL(=2), respectively. The two-determinat CC method for open-shell singlet states can be activated by TD-CC (=8). (Default: SPIN-ORBITAL).

This specifies the maximum allowed number of geometry optimization cycles. (Default : 50)

This keyword is used in non-HF calculations to specify semicanonical orbitals are used. ``Semicanonical'' orbitals are obtained by diagonalizing the occupied-occupied and virtual-virtual blocks of the spin-orbital Fock matrix and can be advantageously exploited in certain post-SCF calculations (particularly for ROHF-MBPT and non-iterative triple excitation corrections). There is no specific default value for this parameter, and considerable logic is used internally to choose the orbital type in post-SCF non-HF calculations if the keyword is not included. It is strongly recommended that this keyword not be used by anyone who is not thoroughly familiar with non-HF CC/MBPT methods, since the logic used to set the default value is sound. STANDARD (= 0) uses the orbitals obtained in the reference function calculation without modification; SEMICANONICAL (= 1) forces a transformation to semicanonical orbitals; LOCAL (=2) requests a localization of the HF orbitals (currently done according to the Pipek-Mezey localization criterion) (Default : See above).

The keyword STANDARD means that the gradient formulation assumes that the perturbed orbitals are not those in which the Fock matrix is diagonal. CANONICAL means that the perturbed orbitals are assumed to be canonical. This keyword must be set to CANONICAL in derivative calculations with methods which include triple excitations (MBPT[4], CCSD+T[CCSD], CCSD[T], QCISD[T] and all iterative schemes like CCSDT-n and CC3).

For testing purpose, it is possible to force the use standard perturbed orbitals even in case of triple excitations via the option FORCE_STANDA.

Note also that in case of unrelaxed derivatives standard orbitals must be used.

(Default : STANDARD for all methods without triples, CANONICAL for all with triples in case of relaxed derivatives).


Specifies either single (=1, or SINGLE) or double (=2, DOUBLE) sided numerical differentiation in the finite difference evaluation of the Hessian. Two-sided numerical differentiation is considerably more accurate than the single-sided method and its use is strongly recommended for production work. (Default: DOUBLE).

Controls the amount of printing in the energy and energy derivative calculation programs. Using a value of 1 will produce a modest amount of additional output over the default value of 0, which includes some useful information such as SCF eigenvectors, Fock matrix elements, etc. (Default : 0; Value must be specified as an integer).

Specifies whether one-electron properties are to be calculated at the end of the run. OFF (=0) Do not compute properties, FIRST_ORDER(=1) compute first-order properties (dipole moment, qudrupole moment, electrical field gradients, spin densities, etc., SECOND_ORDER(=2). Compute second-order properties (polarizabilities), NMR(=3) compute NMR chemical shifts using GIAOs, CONVENTIONAL(=5): compute magnetic susceptibilities and NMR chemical shifts using field-independent basis functions (this is not recommended). DYNAMICAL(=7) allows the calculation of frequency-dependent polarizabilities (available at SCF and unrelaxed CCSD level). Indirect spin-spin coupling constants are available via J_SO(=8), i.e., this gives the spin-orbit contribution to J, J_FC(=9), i.e., this yields the Fermi-contact contribution, and J_SD(=10), which gives the spin-dipole contribution to J. For testing purposes, the option NMR_SWITCH (=4, which treats the nuclear magnetic moments as perturbation in the CPHF equations and does not use GIAOs) is available, but this option is not recommended for routine application and yields gauge-origin dependent results. RESPONSE (=13) requests calculation of linear and quadratic response properties and requires special input. (Default : 0).

This keyword allows storage of property integrals computed in vdint on ``internal files'' (e.g. MOINTS and GAMLAM, option INTERNAL, =1) or on ``external files'' (option EXTERNAL =1) (Default : 0).

The presence of this keyword specifies that a QRHF-based coupled cluster calculation is to be performed. In this method, an SCF calculation is first performed on a closed-shell state specified by either the OCCUPATION keyword or the CHARGE and MULTIPLICTY keywords. Using the closed-shell state orbitals, a coupled-cluster calculation is then performed on an open-shell state generated from this closed-shell state by removing, adding, or exciting electrons. Any number of electrons may be added to the $\alpha$ spin orbitals, and any number may be removed from the $\beta$ orbitals. If QRHF_GENERAL appears as QRHF_GENERAL=0, then a newly-implemented input procedure is used which is described in the section of this manual entitled ``Running QRHF-CC calculations''. Otherwise, the older input is used, which is described below. Any integers associated with this keyword must be separated by slashes ``/'' and take on either negative (for removal of $\beta$ electrons) or positive (addition of $\alpha$ electrons) integer values. The absolute values of these parameters specify the symmetry block(s) involved in the addition or removal of electrons. The numerical ordering of the symmetry blocks is consistent with that used in specifying the orbital occupations. By default, the electrons are added to the lowest unoccupied molecular orbital in the symmetry block and removed from the highest occupied molecular orbital. Different orbitals may be specified with the QRHF_ORBITAL keyword (see below).

NOTE: Gradients and property calculations are currently available only for cases involving addition or removal of electrons. Mixed cases involving both processes have not yet been coded, and may never be...

By default, in QRHF calculations, electrons are removed from the highest occupied orbital in a symmetry block (symmetry block HOMO), while electrons are added to the lowest unoccupied orbital within a symmetry block (symmetry block LUMO). The purpose of the QRHF_ORBITAL keyword is to allow additional flexibility in choosing which orbitals will have their occupation numbers altered. The value of this keyword gives the offset with respect to the default orbital for the orbital which will be depopulated (or populated) in QRHF-CC calculations. For calculations involving more than one removal or addition of electrons, values are separated by commas and correspond to the QRHF_GENERAL input on a one-to-one basis. For example, specifying QRHF_GENERAL=2/-4,QRHF_ORBITAL=3/2 means that an electron will be added to the third lowest virtual in symmetry block 2 and another will be removed from the second highest occupied orbital in symmetry block 4. Examples given later in this manual further illustrate the QRHF input options and may help to clarify any confusion resulting from this documentation. (Default : 1)

This keyword specifies the spin of the electrons modified by the QRHF_GENERAL and QRHF_ORBITAL keywords, where a value of 1 means $\alpha$ spin, while 2 corresponds to a $\beta$ electron. By default, electrons that are removed are assigned to $\beta$ spin, while added electrons are $\alpha$. Note that this option allows one to construct low-spin determinants, which generally are unsuitable for single-reference coupled-cluster calculations. An important exception is the open-shell singlet coupled-cluster method (see keyword OPEN-SHELL=TD-CC above).

Specifies whether or not relaxed density natural orbitals are to be computed. This option only has meaning for a correlated calculation. =0 Do not compute, =1 compute. (Default: 1).

The type of SCF calculation to be performed. RHF (= 0) restricted Hartree-Fock reference; UHF (= 1) unrestricted Hartree-Fock reference=1; ROHF (= 2) restricted open-shell Hartree- Fock calculation; TWODET (=3) two-determinant reference for open-shell singlet CC calculations, ROHF-OS (=4) restricted open shell singlet Hartree-Fock reference for OS-CC calculations (NCI) (Default : 0).

Specifies whether the relaxed density matrix is computed for correlated wave functions. OFF (= 0) The relaxed density will not be computed, ON (= 1) it will be computed. (Default : 0).

This option can be used to convert an analytically calculated gradient vector to a particular normal coordinate representation. A useful application is to calculate the gradient of an electronically excited state in the normal coordinate representation of the ground electronic state, as this provides a first approximation to resonance Raman intensities (hence the name of the keyword). Calculations that use the RESRAMAN option require the externally supplied force constant matrix FCMFINAL, which is written to disk during the course of both analytic and finite-difference vibrational frequency calculations. No such transformation is performed if OFF (=0); while ON (=1) directs the program to evaluate the gradient and transform it to the chosen set of normal coordinates. A warning message is printed if the force constant matrix is unavailable. (Default : OFF)

This keyword offers the possibilty to restart a CC calculation which stopped for various reasons, e.g. time limit, in the correlation part. However, note that a restart which is specified by ON (= 1) needs the following files of the previous unfinished calculation: JOBARC, JAINDX, MOINTS, and MOABCD. (Default : OFF)

This keyword specifies which eigenvector of the orbital rotation Hessian is to be used to rotate the original SCF orbitals. By default, it will use that associated with the lowest eigenvalue of the totally symmetric part of the block-factored Hessian, as this choice often leads to the lowest energy SCF solution. For RHF stability checks, only those instabilities which correspond to RHF solutions will be considered. It is important to understand that following non-symmetric eigenvectors lowers the symmetry of the wavefunction and that following RHF$\rightarrow$UHF stabilities leads to a UHF solution. To converge the SCF roots associated with such instabilities, one must run the calculation in reduced symmetry and as a closed-shell UHF case, respectively. ROT_EVEC=n directs the program to follow the vector associated with the n$^{th}$ lowest eigenvalue having the proper symmetry (totally symmetric) and spin (RHF$\rightarrow$RHF or UHF$\rightarrow$UHF) properties. (Default : 0 [use the lowest eigenvalue])

Switch which tells ACES II whether to delete large files (AO integrals and MOINTS file for now) when they are no longer needed. OFF (= 0) They will not be saved, ON (= 1) they will be saved. (Default : 0).

Controls whether step scaling is based on the absolute step length (1-norm) (=0 or MAG(S)) or the largest individual step in the internal coordinate space (=1 or MAX(S)). (Default: MAG(S)).

The convergence criterion for the SCF equations. Equations are considered converged when the maximum change in density matrix elements is less than $10^{-N}$. (Default : 7).

This keyword controls the damping (in the first iterations (specified by SCF_EXPSTART) via D(new) = D(old) + X/1000 * [D(new) - D(old)] with X as the value specified by the keyword. The default value is currently 1000 (no damping), but a value of 500 is recommended in particular for transition metal compounds where the SCF convergence is often troublesome.

Specifies the number of density matrices to be used in the DIIS convergence accelaration procedure. =N N density matrices will be used. (Default : 6).

Sets the latest iteration for initiation of the DIIS convergence acceleration procedure in SCF calculations. DIIS is switched on when the error falls below a certain threshold, but in difficult cases where the iterations are oscillatory it is necessary to force it on when the error is still large. In such a case, the RPP will begin on the iteration number specified by this parameter. (Default : 15).

Specifies whether or not the DIIS extrapolation procedure is to be used to accelarate convergence of the SCF equations. =0 Do not use DIIS, =1 use DIIS. (Default : 1).

Specifies the maximum number of SCF iterations. (Default : 150).

This keyword is no longer in use.

Specifies the strength of a spin-dipole pertubation as required for finite-field calculations of the SD contributions to indirect spin-spin coupling constants. The value must be specified as an integer and the SD strength used by the program will be the value of the keyword $x 10^{-6}$. (Default : 0, currently not implemented)

This keyword specifies whether spherical harmonic (5d, 7f, 9g, etc.) or Cartesian (6d, 10f, 15g, etc.) basis functions are to be used. ON (= 1) uses spherical harmonics, OFF (= 0) uses Cartesians. (Default : ON).

This keyword controls whether excitation energy calculations allow for a ``spin flip'' which changes the $M_s$ quantum number. Such calculations have some advantages for biradicals and are currently implemented (together with gradients) for CIS and CIS(D) calculations. Options are OFF and ON. (Default : OFF).

This keyword allows the user to specify a specific Abelian subgroup to be used in a calculation. Acceptable arguments are DEFAULT (=0); C1 (= 1); C2 (= 2); CS (= 3); CI (= 4); C2V (= 5); C2H (= 6); D2 (= 7) and D2H (= 8). Use of C1 is of course equivalent to setting SYMMETRY=OFF in the input. The DEFAULT option (which is the default) uses the highest order Abelian subgroup (Default : 0).

This is a somewhat complicated keyword to use. Allowed values are the integers 1, 2 and 3, which specify the $x$,$y$ and $z$ axes, respectively. The meaning of the keyword is best described by example : Suppose one is running a calculation on water, and wishes to run it in the $C_s$ point group with the ``special'' plane being the one which bisects the H-O-H bond angle. Now, what SUBGRPAXIS does is to specify which Cartesian direction in the $C_{2v}$ frame becomes the special direction in the $C_s$ frame. ACES II will orient water in the $yz$ plane, so one wants the $y$ axis in the $C_{2v}$ frame to be the $z$ axis in the $C_s$ frame. Hence, for this case, one would specify SUBGRPAXIS=2. Use of this keyword may be facilitated by studying section D1 of this chapter, entitled ``Molecular Orientation''. However, when the true Abelian subgroup is either $C_{2v}$ or $D_{2h}$, the ACES II orientation is not well defined, and it may be necessary to run the XJODA executable directly two times. If SUBGROUP=0 in the first pass, then the reference orientation for the true Abelian subgroup can be determined and the appropriate value of SUBGRPAXIS selected.

This is a new and somewhat imperfectly implemented option that in principle can be used to force the SCF to converge a solution for which the density matrix transforms as the totally symmetric representation of the point group (i.e. no broken symmetry solutions). The code seems to work in most cases, but has currently been implemented for point groups with E type representation and not for those with triply-, quadruply- or pentuply-degenerate representations. Extending the code to those cases is probably straightforward, and the reader is encouraged to do so if (s)he is so inclined. SYM_CHECK=0 ``forces'' the high-symmetry solution; SYM_CHECK=OVERRIDE (= 1) doesn't. The latter is the default.

Specifies what subgroup of the full point group is to be used in the energy and/or gradient calculation (The `` computational" point group). OFF (=1) forces a no symmetry run (in $C_1$), ON (=0) runs the calculation in the largest self-adjoint subgroup ($D_{2h}$ and its subgroups), and FULL (=2) uses the full point group. Currently, ACES II does not support groups with degenerate representations, so the FULL option has no value unless Joda is being used to make input decks for another program package. However, the the algorithm which determines the number of gradients to be evaluated and performs the resulting construction of the force constant and dipole derivative matrices uses the full point group symmetry. NOTE: In the vast majority of cases, the general user should not need to use this keyword. Exceptions include error detection (for example, to see if an incorrect result or a program crash occurs with and without symmetry), and some calculations in the presence of finite fields.

Specifies how often the largest t amplitudes are to be printed. =0 Amplitudes are printed at the beginning and end of the run, =1 Amplitudes are printed every iteration, =2 Amplitudes are printed every other iteration, etc. (Default : 5).

This keyword specifies whether or not translational invariance is exploited in derivative calculations. USE(=0) specifies that translational invariance is exploited, while IGNORE (=1) turns it off. (Default : USE)

This keyword is used for certain types of correlated second derivative calculations [presently only GIAO NMR shift calculations] and directs ACES II to either treat all perturbations at once or treat them sequentially. The latter approach results in less demand for physical disk space, but at the cost of increased cpu time. Available options are SIMULTANEOUS (=0); and SEQUENTIAL (=1). (Default : SIMULTANEOUS).

This keyword specifies the threshold value (given as an integer) for the treatment of CPHF coefficients in second derivative calculations using perturbed canonical orbitals. If a CPHF coefficient is above the threshold, the corresponding orbital rotation is treated (at tyhe expense of additional CPU cost) using the standard non-canonical procedures, while orbital pairs corresponding to CPHF coefficients below the threshold are treated using perturbed canonical representation. (Default: 25)

Specifies the units used for molecular geometries using the Cartesian coordinate format (see entry for COORDINATES). ANGSTROM (= 0) uses Ångström units, BOHR (= 1) specifies atomic units. (Default : ANGSTROM)

For vibrational frequency calculations. A value of 1 (or EXACT) means perform normal mode analysis on an analytic force constant matrix and computes rotationally projected frequencies and infrared intensities. A value of 2 (or FINDIF) signals ACES II to compute the force constant matrix by finite difference of analytically computed gradients or energies using symmetry-adapted mass-weighted Cartesian coordinates (see entries for keywords FD_CALCTYPE, FD_PROJECT and FD_USEGROUP). (Default: NO)

This keyword defines what type of integral transformation is to be performed in the program VTRAN. FULL/PARTIAL (=0) allows the transformation program to choose the appropriate type of transformation, while FULL (=1) requires a full integral transformation and PARTIAL (=2) means an MBPT(2) Specific transformation where the (ab $\vert$ cd) integrals are not formed. functions. (Default : FULL/PARTIAL)

The tolerance for storing transformed integrals. Integrals less than $10^{-N}$ are neglected and not stored on disk. (Default: 11).

Specifies the X-component of an external electric field. The value must be specified as an integer and the field used by the program will be the value of the keyword $x 10^{-6}$. This allows field strengths $\vert{\cal E}\vert > 10^{-6}$ to be used. (Default : 0)

Specifies the Y-component of an external electric field. See above. (Default : 0)

Sets the convergence criterion for the solution of the ${\cal Z}$ equations in EOM-CC gradient calculations. For ZETA_TYPE=DIIS, the equations are considered converged when the largest element of the residual vector falls below 10$^{-X}$, where $X$ is the value associated with ZETA_CONV; convergence for ZETA_TYPE=POPLE is declared when the norm of the residual vector falls below 10$^{-X}$. (Default : 7 DIIS; 14 for POPLE)

Determines the algorithm used to solve the ${\cal Z}$ equations of EOM-CC gradient theory. POPLE (=0) uses Pople's method of successively orthogonalized basis vectors, while DIIS (=1) uses Pulay's DIIS method. The latter offers the practical advantage of requiring much less disk space, although it is not guaranteed to converge. (Default : DIIS)

Specifies the Z-component of an external electric field. See above. (Default : 0)

The job control parameters are entered following a mandatory blank line at the end of the parameter input section (see above). Delimiters separating individual keywords can be commas (`` ,"), semicolons (`` ;") or ampersands (`` SPMamp;"). To gain some familiarity with the keyword input, try to see how each of the following specifications is equivalent:




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Next: Non-standard Basis Set Specification Up: The ZMAT File Previous: Ghost atoms
root 2004-02-05