[CPMD-list] FREE ENERGY CALCULATION

[Axel Kohlmeyer]

dear fafa,

please see the cpmd manual and the mailing list archives
on additional help for the (many) flags you need to set
for that part of the CPMD code. this part is not as frequently
used as others, so there are a few more rough edges...

on the ATRHO warning: cpmd creates an initial atomic guess
only for the occupied states. for the FEMD module to work
you need a few empty states (between 10 and 20% of the total
number of states. cpmd only adds the minimal amount, so for
cells with a small number of atoms, you may set NSTATES to
a larger number, also you may want to tune the various lanczos
options to get better convergence) and those have to be
initialized, too. this can be either done by providing the corresponding
wavefunction information in the &BASIS section or you can
avoid the issue entirely by starting from a random wavefunction.

as you can see from the significant occurance of fractional
occupations in some bands, this should give you a better
representation of the physics of your system. please also
have a look at the electron temperature parameter that basically
controls the 'amount of smearing' of the kpoints and thus
governs the k-point convergence versus accuracy relation.

cheers,
   axel.


-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
  Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.