Vibrational Analysis

[Ali]

Thanks Flo.

That was very helpful.

Ali

On Jun 24, 3:44 am, flo <fsch... at pci.uzh.ch> wrote:
> Hi Ali,
>
> yes you can get the frequency which is associated with these four
> atoms but you forgot a keyword. maybe for to claryfy for everbody who
> may read this topic I will just explain the different keywords in your
> input file:
>
> &VIBRATIONAL_ANALYSIS
> ! important!!! if you specify the keyword intensities you will have to
> add the
> ! keyword for evaluating dipoles in the FORCE_EVAL section
>
> FULLY_PERIODIC T
>  ! Only important for a full vibrational analysis
>
> !NPROC_REP 2
> ! Important for multiprocessor runs with n processors. It will
> perform
> ! n(processors)/nproc_rep calculations at the same time.
> ! with mode_selective a block davidson algorithm is started.
>
> &MODE_SELECTIVE
> FREQUENCY 500
> ! frequency you want to track (as Ali said:
> !      using Frequency, Range and Involved
> !      atoms are mutually exclusive)
> ! in your case Ali, you will have to use involved_atoms  115 117 120
> 122
> ! to get the frequency associated with these atoms
>
> ATOMS 115 117 120 122
> ! atom numbers for the initial guess (might help to converge faster).
> ! For the initial guess a random vector is construct only having
> components
> ! on these atoms
>
> EPS_MAX_VAL 1.0E-07
> ! convergence criterium for the Davidson algorithm.
> ! The default is already tight enough, since the second derivative is
> evaluated analytically.
>
> &END
>
> For you it means jsut remove frequency and add INVOLVED_ATOMS 115 117
> 120 122.
>
> One importtant point for your calculation might be:
> Since I haven't removed the translations and rotations from the
> algorithm (in this algorithm it's a bit more difficult), I restricted
> the frequencies for the involved atoms part to values >400cm-1
> (otherwise you will many times get the translations). Maybe your
> frequency is lower. Just to be sure, you will get it, you can change
> the code as follows:
>
> grep '400' mode_selective.F
> everywhere it occures just change the value to the threshold you want
> and compile cp2k (should be fast, because it's a tiny change).
>
> Hope this helps
> Flo