Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly  
We are NATO-free zone

Re^7: Clarification required in plotting DOS and IR spectra when SBKJC is used..

Alex Granovsky

Dear Siddheshwar,

provided basis sets are adequate, there should not be large
differences in frequencies computed using different basis sets.
Normally one could expect difference of up to several cm-1.
A difference of 100 cm-1 is very huge and most likely indicates
problems with inadequate basis set etc...

Kind regards,
Alex Granovsky

On Wed Jul 9 '14 2:39pm, Siddheshwar Chopra wrote
>Dear Alex,
>Thank you for the information. Being a physicist, DOS seems more appealing to me, no other particular reason. Sir, could the variation in IR be around at max 100 cm-1 or so when SBKJC and non-SBKJC IR are compared? Again thanks for all the precious information regarding SBKJC. This is something only this forum could have provided.

>Kind Regards,

>On Wed Jul 9 '14 1:51pm, Alex Granovsky wrote
>>Dear Siddheshwar,

>>when I wrote that there would not be any changes in IR I only meant
>>that you need not to explicitly take into consideration ECPs while
>>dealing with IR data as opposed to HOMO-LUMO gap. Sure IR computed
>>with ECP basis set will differ from that of computed with non-ECP
>>basis set. This is normal if the ECP in use is adequate. In this
>>case one can expect small difference between two spectra.
>>The same is true for TDDFT spectra and dipole moments.

>>> So we can't get full DOS when SBKJC is used. Is there any workaround to that Sir?

>>Why exactly do you need DOS? Normally, people is not interested in
>>the DOS contributions due to core electrons. May it be the case that
>>valence DOS is OK for your purposes?

>>Kind regards,
>>Alex Granovsky

>>On Wed Jul 9 '14 11:15am, Siddheshwar Chopra wrote
>>>Dear Alex,
>>>Thank you for confirming no change in IR. So we can't get full DOS when SBKJC is used. Is there any workaround to that Sir? because I wish to use SBKJC for sure. Could you tell what will happen to the TDDFT spectra? Does it change or remains same like IR? Also dipole moment?
>>>Kind Regards,  

>>>On Wed Jul 9 '14 6:51am, Alex Granovsky wrote
>>>>Dear Siddheshwar,

>>>>There should not be any change in the IR spectra.

>>>>As to DOS, as far as I understand you'll get the DOS of
>>>>valence electrons as core electrons are removed. I do not
>>>>know anything on GAUSSUM so I'd suggest to ask GAUSSUM
>>>>developers directly on any compatibility issues.

>>>>Kind regards,


>>>>On Mon Jul 7 '14 12:11pm, Siddheshwar Chopra wrote

>>>>>No Sir there is no problem with the o/p file. I just wish to know DOES GAUSSSUM PLOT THE ACTUAL SPECTRA by default, when SBKJC is used? This doubt is due to the fact that core electrons are removed and as Alex sir explained earlier, the actual HOMO,LUMO are different. Is there any change in the DOS or IR spectra (opened in GAUSSSUM) when SBKJC is used?


[ Previous ] [ Next ] [ Index ]           Tue Jul 15 '14 4:26pm
[ Reply ] [ Edit ] [ Delete ]           This message read 685 times