Recommendations For The Calculation Of Frequency-Dependent Polarizabilities
Orbital relaxed vs orbital unrelaxed calculations
As the calculation of frequency-dependent properties is affected by the pole-structure of the corresponding quantum chemical model, coupled-cluster calculations of these properties should be always carried without consideration of orbital relaxation (keyword: DIFF_TYPE=UNRELAXED), as in this way detoriation of the results due to the presence of the HF poles is avoided. Note that in this way, corresponding calculations are only possible at CC2, CCSD, CC3 levels and, for example, not at the popular CCSD(T) level. Note also that calculation at the MPn levels are also not available.
Large scale calculations should be performed, if possible, using partial AO-algorithms (keyword: ABCDTYPE=AOBASIS, available for CCSD but not for CC3) and the module xecc (keyword: CC_PROG=ECC).
Frozen-core orbitals can be used in all CC calculations of frequency-dependent polarizabilities
There exist the possibility to perform the corresponding CC2 calculations with CFOUR, but please note that CFOUR does not provide an efficient implementation for this CC model.
Currently, it is only possible to perform the calculation for one frequency.
The calculated frequency-dependent polarizability tensor can be also found on the file DPOLAR