[CPMD-list] questions on PIMD

[Serge Ivanov]

    Hi !

 There are obviosly problems with what you are trying to do.
1) The temperature of 600K is not the interesting one for applying PI
   formalism, since the system behaves classically being heated that much.
2) Don't use massive thermostat for electrons. 
3) Before applying centroid dynamics, one should study the Trotter
   convergence for given system using 'regular' PI dynamics.
4) Centroid dynamics will require a much smaller time step, than the
   classical one. One also has to provide two adiabaticity levels, i.e.
   between centroid and other beads and between other beads and electrons.
   You can read this and other connected issues in more detail, e.g. in 
   Marx,Hutter book here:

   http://www.theochem.ruhr-uni-bochum.de/research/marx/cprev.en.html

5) You should always check how stable is your Verlet scheme, at least,
   by looking at the conserved quantity (9th column in the ENERGIES file
   for PI). I'm pretty sure that your current runs are very unstable.

WBR, Serge   

On Fri, 9 Mar 2007, qfzhang wrote:

> Date: Fri, 09 Mar 2007 10:13:18 GMT
> From: qfzhang <qfzhang at aphy.iphy.ac.cn>
> To: cpmd-list at cpmd.org
> Subject: [CPMD-list] questions on PIMD
> 
> Hi,dear all!
>   I want to use centroid PIMD in periodic oxide system. and the energy of the
> w
> hole system is about 1000 Hatree.But the EKINC/P term in the output file, i.e
> th
> e electron kenetic energy, is always very high, about 0.2 Hatree. Even after
> lon
> g-time equilibrium, it still will rise rapidly when beginning the PIMD
> simulatio
> n.Is there any trick to solve the problem? the input file is as below.
> 
> &CPMD
> PATH INTEGRALS
> MOLECULAR DYNAMICS CP RESTART WAVEFUNCTION COORDINATES VELOCITIES LATEST
> TEMPERATURE
> 600.d0
> NOSE IONS MASSIVE
> 600.d0   5000.d0
> NOSE ELECTRONS MASSIVE
> 0.012  18000.d0
> 
> CONVERGENCE ORBITALS
> 1.0E-04
> EMASS
> 150
> MAXSTEP
> 7500 TIMESTEP
>  2.0
> TRAJECTORY XYZ SAMPLE
> 1
> 
> &END
> 
> &DFT
> NEWCODE
> FUNCTIONAL BLYP 
> &END
> 
> &SYSTEM
> ANGSTROM
> SYMMETRY
> 1 CELL
> 8.52 1.0 1.0  0  0  0
> CUTOFF
> 100.0
> CHARGE
> 1.0
> &END
> 
> 
> &ATOMS
> ........
> ........
> CONSTRAINTS
> FIX STRUCTURE 1
> DIFFER 23 41 24  -0.7287
> END CONSTRAINTS             
> &END
> 
> &PIMD
> CENTROID DYNAMICS
> TROTTER DIMENSION
>  8 NORMAL MODES
>  50.0
> FACMASS
>  1.0
> PRINT LEVEL
>  1
> PROCESSOR GROUPS
> 1
> &END
> 
> 
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