[CPMD-list] help regarding PIMD

[Axel Kohlmeyer]

On Fri, 16 May 2008, Tuhina Kelkar wrote:

TK> Hello Everyone!

hello tuhina,

[...]

please see the recent (lengthy) discussion thread on PIMD 
wrt to the necessity of keeping the thermostat on the 
electrons turned off until all other parameters are chosen
correctly and you have a stable CP dynamics.

TK> way different from those obtained from the CPMD simulations.
TK> 
TK> I am unable to understand that while the energies at each step match their
TK> averages do not. Could someone help me in this regard? Why is this
TK> happening? Are these averages calculated differently? I am copying below the

please help yourself to reading the source code! or find somebody
that has the time to do it for you...
the place where those averages are computed can be easily found.

TK> input files (minus the ATOMS section) and average quantities obtained from
TK> the 2 simulations for you to see.

as stated _many_ times, if you want people to look into 
your problem, you have to make it easy to reproduce it. 
again, just see how lukasz has been handling it. 

cheers,
    axel.


TK> 
TK> With regards,
TK> Tuhina
TK> 
TK> (1) &INFO
TK> mgh2
TK> stage 4 of CPMD
TK> &END
TK> &CPMD
TK> MOLECULAR DYNAMICS CP
TK> RESTART COORDINATES WAVEFUNCTION LATEST
TK> RESTART NOSEP NOSEE
TK> RESTART VELOCITIES
TK> TIMESTEP
TK> 5.0
TK> NOSE IONS
TK> 300 2000.0
TK> NOSE ELECTRONS
TK> 0.006 9000
TK> TRAJECTORY SAMPLE XYZ
TK> 5
TK> PRINT
TK> 20
TK> MAXSTEP
TK> 500
TK> EMASS
TK> 400
TK> &END
TK> &DFT
TK> FUNCTIONAL GGA (=PW91)
TK> &END
TK> &SYSTEM
TK> SYMMETRY
TK> 6
TK> SCALE
TK> CELL ABSOLUTE DEGREE
TK> 16.9730 16.9730 11.3209 90.0 90.0 90.0
TK> CUTOFF
TK> 35
TK> &END
TK> 
TK> 
TK>  ****************************************************************
TK>  *                      AVERAGED QUANTITIES                     *
TK>  ****************************************************************
TK>                               MEAN VALUE       +/-  RMS DEVIATION
TK>                                      <x>     [<x^2>-<x>^2]**(1/2)
TK>  ELECTRON KINETIC ENERGY    0.594767E-02             0.705827E-03
TK>  IONIC TEMPERATURE                288.11                    24.69
TK>  DENSITY FUNCTIONAL ENERGY    -33.122802             0.642653E-02
TK>  CLASSICAL ENERGY             -32.995247             0.692273E-03
TK>  CONSERVED ENERGY             -32.989299             0.200328E-04
TK>  NOSE ENERGY ELECTRONS          0.006899             0.146511E-02
TK>  NOSE ENERGY IONS               0.056337             0.509951E-02
TK>  CONSTRAINTS ENERGY             0.000000              0.00000
TK>  ION DISPLACEMENT           0.219204                 0.859291E-01
TK>  CPU TIME                         0.4549
TK>  ****************************************************************
TK> 
TK> (2)&INFO
TK> mgh2
TK> pimd under classical test
TK> &END
TK> &CPMD
TK> MOLECULAR DYNAMICS CP
TK> PATH INTEGRAL
TK> RESTART COORDINATES WAVEFUNCTION LATEST
TK> RESTART NOSEP NOSEE
TK> RESTART VELOCITIES ACCUMULATORS
TK> TIMESTEP
TK> 5.0
TK> NOSE IONS
TK> 300 2000.0
TK> NOSE ELECTRONS
TK> 0.006 9000
TK> TRAJECTORY SAMPLE XYZ
TK> 5
TK> PRINT
TK> 20
TK> MAXSTEP
TK> 500
TK> EMASS
TK> 400
TK> &END
TK> &PIMD
TK> CLASSICAL TEST
TK> &
TK> &DFT
TK> FUNCTIONAL GGA (=PW91)
TK> &END
TK> &SYSTEM
TK> SYMMETRY
TK> 6
TK> SCALE
TK> CELL ABSOLUTE DEGREE
TK> 16.9730 16.9730 11.3209 90.0 90.0 90.0
TK> CUTOFF
TK> 35
TK> &END
TK> 
TK>  ****************************************************************
TK>  *                      AVERAGED QUANTITIES                     *
TK>  ****************************************************************
TK>                               MEAN VALUE       +/-  RMS DEVIATION
TK>                                      <x>     [<x^2>-<x>^2]**(1/2)
TK>  ELECTRON KINETIC ENERGY     313.214                  313.214
TK>  IONIC TEMPERATURE                205.79                   131.82
TK>  DENSITY FUNCTIONAL ENERGY    287.379817              286.013
TK>  QUANTUM KINETIC ENERGY(P)      0.047852             0.302409E-01
TK>  QUANTUM KINETIC ENERGY(V)  25492.050728              25492.1
TK>  TOTAL QUANTUM ENERGY(P)      -23.611303              14.9331
TK>  CLASSICAL ENERGY             287.357202              286.001
TK>  CONSERVED ENERGY             -23.563769              14.9031
TK>  ION DISPLACEMENT           0.230188                 0.291464E-01
TK>  CPU TIME                         0.4532
TK> 
TK> ---------------------------------------------------------------------------
TK> Tuhina Kelkar
TK> c/o Dr. Sourav Pal
TK> Physical Chemistry Division,
TK> National Chemical Laboratory,
TK> Pune - 411008
TK> INDIA
TK> -----------------------------------------------------------
TK> 

-- 
=======================================================================
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.