Re: CCL:Crystal structure vs geometry optimised structure

[John Bushnell <bushnell/at/chem.ucsb.edu>]

For doing frequency calculations, you will want to use the DFT
 optimized structures, as the calculation won't be very meaningful
 otherwise.  You should only be calculating frequencies at a minimum.
 If your DFT structures are in excellent agreement with your crystal
 structures, you are probably better off using the DFT optimized
 structures for energy comparisons as well.  Of course, if in certain
 cases your DFT optimized structures were fundamentally different from
 the crystal structures, the DFT energy comparison might not make much
 sense if you are trying to examine the energetic differences between
 your (crystal) samples.
   Hope that helps  -  John
 On Wed, 23 Jul 2003 noel.oboyle2/at/mail.dcu.ie wrote:
 > Hello CCLers,
 > I intend to carry out DFT calculations on inorganic complexes. In some
 cases
 > I have crystal structures available.
 >
 > Is it better to use crystal structures as a starting point for energy
 > and frequency calculations, or to use DFT-optimised structures? (where
 > the DFT-optimised structure is in excellent agreement with the crystal
 > structure)
 >
 > Thanks,
 > Noel O'Boyle
 > Han Vos Research Group,
 > Dublin City University.
 >
 >
 >
 >
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