Christian Seifert wrote:
On Friday 22 June 2007 11:22, Lars Schaefer wrote:
Hi Christian,
I am not sure what exactly you need the Hessian for. But if you are
interested in IR spectra, you might also calculate them from dipole
autocorrelation (instead of from the hessian).
Best,
Lars
You are right. We are interested in IR spectra calculated by GMX/CPMD. We have
already done this with EGO/CPMD. Obviously it is not possible to calculate a
hessian of a subsystem with gromacs.
A complete QM/MM Hessian contains, apart from the rather straightforward
QM/QM and MM/MM parts also the mixed blocks (see e.g. paper below). So:
No, QM/MM second derivatives is not implemented in GROMACS (yet).
Best,
Lars
author={Q.~ Cui and M.~ Karplus},
title={Molecular properties from combined QM/MM methods. I. Analytical
second derivative and vibrational calculations},
journal={J. Chem. Phys.},
volume={112},
number={3} ,
pages={1133-1149},
year=2000
Thus we have to calculate the IR spectra
from dipole autocorrelation.
Thanks to all of you for your help
Christian.
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