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Re^3: Problem with Hessian and TDDFT calculations..

Thomas Pijper
thomaspijper@hotmail.com


Dear Siddheshwar,

A few comments:

$SCF NCONV=8 is very tight, I'd say that the default NCONV=5 would be sufficient in your case.

$TDDFT NSTATE=100 is a lot of states. I expect that 30 to 40 states is enough if you are trying to obtain a UV/vis spectrum. This should speed up your calculation significantly.

$CONTRL INTTYP=HONDO ICUT=11 ITOL=30 should not be necessary (unless you are calculating a numerical gradient). Same goes for $DFT LMAX=41 NRAD=99. This will help in speeding up your calculation.

$BASIS GBASIS=N31 NGAUSS=6 is a very light basis set. I would at least try to add NDFUNC=1 (resulting in the 6-31G(d) basis).


Kind regards,
Thom



On Tue Mar 4 '14 10:07am, Siddheshwar Chopra wrote
--------------------------------------------------
>Dear Sir,
>Thank you for pointing out this silly mistake of mine. I will note this down now. As for the TDDFT calculations please find attached the i/p file. I have used the lowest energy state coordinates for the same. Please have a look at it.

>Regards,

>On Mon Mar 3 '14 5:51pm, Thomas Pijper wrote
>--------------------------------------------
>>Dear Siddheshwar,

>>> I ran HEssian calculations on my sample first. I
>>> got NO imaginary frequencies. But I could not find
>>> "Equilibrium geometry located" text anywhere.

>>This is because you specified RUNTYP=HESSIAN. This performs a Hessian calculation. The message "Equilibrium geometry located" appears only with a completed geometry optimization (RUNTYP=OPTIMIZE or SADPOINT). Your geometry does correspond to a minimum on the PES.
>>
>>
>>> I run TDDFT calcs. But in that I am getting this error now:
>>>
>>> * ... LESS THAN �3.000
>>>
>>> **** THERE ARE ATOMS LESS THAN � 0.100 APART, QUITTING... ****
>>
>>
>>Most likely you made an error in the $DATA group of the TDDFT calculation input. It could for example be that you specified a point group other than C1, but specified coordinates corresponding to the C1 geometry, thus causing some atoms to be specified twice. If you would like me to take a closer look at the problem, feel free to post the input file for your TDDFT calculation.
>>
>>
>>Kind regards,
>>Thom
>>
>>
>>
>>
>>
>>On Mon Mar 3 '14 11:21am, Siddheshwar Chopra wrote
>>--------------------------------------------------
>>>Dear Sir,
>>>I ran HEssian calculations on my sample first. I got NO imaginary frequencies. But I could not find "Equilibrium geometry located" text anywhere. Now thinking that it is a global minimum, I run TDDFT calcs. But in that I am getting this error now:

>>> �* ... LESS THAN �3.000

>>> **** THERE ARE ATOMS LESS THAN � 0.100 APART, QUITTING... ****

>>>What is wrong here? What should I do next to rectify this. If the sample was not in global minima, then how come there were no imaginary freqs?

>>>Regards,


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