Dear Colleagues,

I am also interested in calculating dynamic polarizability (plrb) tensor alpha(l,m,l',m') for imaginary frequencies.

I need it for calculating long-range van der Waals dispersion (and induction with multipole moments) coefficients. I have searched the forum and here are some related topics, categorized and with some questions to the Experts and Developers of Dalton. As an example, let's consider the simplest case of atom-atom interaction, Ne dimer. For C6 one would need just alpha(1,0,1,0), dipole-dipole plrb, for C8 both alpha(1,0,1,0) and alpha(2,0,2,0), quadropole-quadropole plrb, and so on.

1. Damped response calculation: *ABSORP
Also discussed here:

http://daltonprogram.org/forum/viewtopic.php?f=9&t=281
http://daltonprogram.org/forum/viewtopic.php?f=9&t=365
In this case .ALPHA is just dipole-dipole plrb and there is now way to find other tensor components.

Also, I did NOT manage to calculate .BETA, dipole-dipole-dipole hyperplrb for imaginary freqs.

It is not needed for disp. coef. at this level of theory, but I was curious. What is wrong in my input? It works well with just .ALPHA. (See attachment 1). As I understand .GAMMA is not yet available.

Do I understand correctly that *ABSORP works only with HF, DFT and MCSCF levels of theory? What about SOPPA(CCSD) with *ABSORP?

It fails (see attachment 2).

2. Cauchy moments with *C6
Keywords - .C6ATM, .C6SPH etc.

Once you have the Cauchy moments, you use eq. (4) from the Ref. given by Hans Jørgen for imaginary

omega, then use Pade aproximants and integrate (calculate Cn disp. coefs).

If I use .C6ATM and .C8ATM then I get the following Cauchy moments

SM01+00 SM01+00 - needed to find dipole-dipole plrb.

SM02+00 SM02+00 - needed to find quadropole-quadropole plrb.

SM02+00 SM01+00 - dipole-quadrupole plrb. (=0 for closed shell atoms)

Using .C10ATM will give higher Cauchy moments SM04+00 SM04+00 that will be needed to find the full C12 coef.

Here are C6 and C8 coefs (a.u.) calculated with hf/avtz:

*ABSORP:

C6= 5.1675, C8=.. (could NOT get it without dynamic quadrupole-quadrupole plrb)

*C6:

C6=5.1879, C8=42.7871, C10=367.1082.

With *C6 one can use SOPPA and SOPPA(CCSD).

3. Dispersion coefficients D_AB(n) found with *CCLR and .DISPCF.
Note that these are different dispersion coefs, not Cn (see 31.3 paragraph of 2016 manual). See also discussion here

http://daltonprogram.org/forum/viewtopic.php?f=9&t=378
The C6 value found with this method is 5.8928. It is a bit different from the one found with *C6 and SOPPA(CCSD) - 5.8414. (avtz basis set)

It looks it works only for dipole-dipole plrb, i.e. with

.OPERATOR

ZDIPLEN ZDIPLEN

There is some disscussion here about how to find quadropole-quadropole plrb

http://daltonprogram.org/forum/viewtopic.php?f=9&t=318
but I didn't manage to.

One can also use *CCQR and *CCCR for finding beta and gama.

4. There is also module *ABALNR that might be useful.

So, resuming method

2 with Cauchy moments is the only way to find all the dispersion coefs, not only C6.

P.S. I used Dalton 2013.3, but these modules were not changed in 2016 version.