Issue using mixed calculation
Francesco Ambrosio
francesco... at epfl.ch
Thu Jan 8 12:20:10 UTC 2015
Dear cp2k users and developers.
I want to use thermodynamic integration (TI) to compute differences in
energies of a Cl vacancy defect in NaCl with two different states of charge
(0 and +1). If my procedure is correct the result obtained by TI
(integration of vertical energy gaps) should equal the result obtained by
energy difference of the energy minima of NaCl(+1) and NaCl(0) relaxed
structures. The latter are easily computed. In order to compute the
vertical energy gaps at intermediate steps, I use a mixed calculation
(input attached). Basically, I aim to optimize the intermediate structures
(at different values of the coupling parameter) and hence compute the
vertical gap from wavefunction optimizations with n and n-1 electrons.
Nevertheless, the results I am obtaining are quite worrying because I
obtain different intermediate optimized geometries if I use as starting
structure the relaxed NaCl(+1) or the NaCl(0) respectively and the final
structures are close to the initial ones. I thought of a possible mistake
of my input but if I set lambda=0 and lambda=1 I recover the correct
optimized structures of NaCl(+1) and NaCl(0), no matter the starting point.
Do you have any thoughts about this based on your experience?
Thank you for your courtesy and your kindness
Francesco
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