[CPMD-list] NVT

[Juerg Hutter]

Hi

On Fri, 11 Jul 2003, Martijn Zwijnenburg wrote:

> Hi,
>
> I'm doing a NVT md run on a small cluster (see for inputfile below)
> and have some questions.
>
> 1) In my md run EHAM is not constant but rather varies from the third
> decimal on. However, since this run employs an NVT ensemble rather
> then an NVE I wonder if EHAM should still be conserved and thus stay
> constant?

EHAM is still a constant of motion. If it's not constant you have to
change the integration procedure. If the system without the
thermostat is integrated without problems, then you have to
change the parameters for the NOSE thermostats. Parameters 5 and 6
(Suzuki integrator and decomposition parameter).


>
> 2) The systems seems to cool down over time. I set the thermostat
> temperature at 1000K but the electron temperature cools down, after a
> small overshoot, to allready 600K after 200 steps. I guess this means
> my thermostat is not working properly?
>

I don't get this. You have a thermostat at the ions only but you are
talking about electron temperature.
If you have a bad drift in EHAM the temperature of the ions and
the kinetic energy of the electrons can vary a lot. However,
the ionic temperature should be on average at the preset value.

Juerg



> Cheers,
>
> Martijn
>
> Inputfile:
>
> ! Si4O8 cluster MD
> !
> &CPMD
>   MOLECULAR DYNAMICS
>   STRUCTURE BONDS ANGLES DIHEDRALS
>   CONVERGENCE
>   1E-6 5E-6 1.
>   ISOLATED MOLECULE
>   HESSIAN UNIT
>   RESTART WAVEFUNCTION GEOMETRY LATEST
>   NOSE IONS
>   1000 800
>   TIMESTEP
>   5.0
>   EMASS
>   700
>   TRAJECTORY XYZ
> &END
> &SYSTEM
>   SYMMETRY
>   0
>   ANGSTROM
>   CELL
>   15 1.0 1.0 0 0 0
>   ANGSTROM
>   CUTOFF
>   30.00
>   POINT GROUP
>   AUTO
> &END
> &ATOMS
> *Si_ps.uspp BINARY new.f
>   LMAX=P
>  4
>    0.000000000000      0.000000000000      0.000000000000
>    0.471809914327      0.000000000000      3.182682023275
>    3.653225710458     -0.034526749450      2.711038719844
>    3.181409275132     -0.034559479116     -0.471644591443
>
> *o_ps.uspp BINARY new.f
>   LMAX=P
>  8
>   0.000000000000      0.000000000000      1.626292446278
>   2.098080331254     -0.016336484977      3.186832736955
>   3.653206618118     -0.034138170947      1.084746035991
>   1.555131813001     -0.018896584142     -0.475808582925
>   4.871737465360     -0.049224011432      3.612939458029
>  -0.432765838343      0.012873808042      4.399223302846
>  -1.218511827443      0.015066749685     -0.901895052361
>   4.086009030180     -0.046817197390     -1.688173543327
>
> &END
> &DFT
>  FUNCTIONAL PW91
>  GC-CUTOFF
>  5E-5
> &END
> ----------------------------------------------------------------------
> ---
> Martijn Zwijnenburg
> Lab. of Applied Organic Chemistry and Catalysis
> Delft University of Technology
> Julianalaan 136
> 2628 BL Delft
> The Netherlands
> Tel: 0031-(0)152782691
> Fax: 0031-(0)152784700
> e-mail: M.A.Zwijnenburg at tnw.tudelft.nl
> web page: http://come.to/tock
>
>
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