[CPMD-list] Energy components in PIMD

[Łukasz Walewski]

Dnia 2008-05-14, śro o godzinie 12:35 -0400, Axel Kohlmeyer pisze:
> 
> dear lukasz,

Dear Axel,

> one thing that came to my mind, is that you may improve the
> situation by turning the "outside" hydrogens into deuterium.
> their bonded vibrations seem to be of pretty high frequency and 
> thus slowing them down by increasing their mass may help improving 
> the stability w.r.t. timestep and ficitious mass.

I performed this test - the situation gets even worse than with "light"
outer hydrogens. In the attached graph black plot is the EKINC from
previous run with VDB/35Ry/3au. and the red plot is EKINC from similar
run with the outer protons substituted with deuterium (see attached
input file).

[...]

> LW> There is one more issue regarding the COM. The second attached plot
> LW> shows the conserved energy, that exhibits jumps every 2500 steps - that
> LW> is every time I SUBTRACT COMVEL ROTVEL. The jumps occur on the fifth
> LW> decimal place in Ha. Would you accept such behavior ? (I know one should
> LW> not rescale velocities when using NH thermostat but the manual is
> LW> equivocal on what is already a bad thing.)
> 
> you can rescale more often, say every 25th step? that would make
> the disruptions smaller (but more frequent).

This seems to me negatively verified - on the second attached graph the
black plot is the total energy with COM motion removal every 10'000
steps and the red plot - every 25 steps. The plots speak for themselves.

Regards,
Lukasz
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&CPMD
  MOLECULAR DYNAMICS CP
  RESTART WAVEFUNCTION COORDINATES LATEST
  REAL SPACE WFN KEEP
   TIMESTEP
    3.0
  EMASS
    200.0
  TEMPERATURE
    300.0
  NOSE IONS MASSIVE
    300.0  1800.0
  MAXSTEP
    137805
  SUBTRACT COMVEL ROTVEL
    25
  TRAJECTORY XYZ SAMPLE
    -10
  ISOLATED MOLECULE
  CENTER MOLECULE
  STORE
    1000
&END

&SYSTEM
  ANGSTROM
  SYMMETRY
    8
  CELL ABSOLUTE
    13.0 13.0 8.0 0.0 0.0 0.0
  CUTOFF
    35.0
&END

&DFT
  FUNCTIONAL BLYP
  GC-CUTOFF
    5.D-6
&END

&ATOMS

ISOTOPES
 14.0067
 12.0112
  2.0000
  1.0080

*N_VDB_BLYP.psp FORMATTED
   LMAX=P
   4
       1.480434744000      -1.261526338000       0.012486679000
      -1.428836888000      -1.263268937000       0.020030520000
      -1.482423266000       1.260607946000       0.012029901000
       1.430161665000       1.261259358000       0.004480994000
*C_VDB_BLYP.psp FORMATTED
   LMAX=P
   20
       2.764321879000       1.617573818000      -0.000125061000
       3.855614684000       0.719804456000      -0.000057419000
       3.883340408000      -0.678014026000       0.004378686000
       2.816852951000      -1.603192445000       0.010125751000
       2.919542448000      -3.046779447000       0.014515219000
       1.637225743000      -3.547145051000       0.019451505000
       0.739381956000      -2.412298909000       0.018118048000
      -0.677939805000      -2.411241253000       0.021787063000
      -1.565841060000      -3.552172948000       0.027767194000
      -2.851571375000      -3.063067365000       0.029521295000
      -2.763080194000      -1.618905630000       0.024634604000
      -3.853925457000      -0.720052370000       0.024562307000
      -3.883570717000       0.678208069000       0.020129751000
      -2.818027537000       1.604764172000       0.014380689000
      -2.917826697000       3.049092800000       0.009981340000
      -1.634343765000       3.546387751000       0.005051935000
      -0.738698022000       2.409860388000       0.006396510000
       0.678687181000       2.408624576000       0.002727905000
       1.566148163000       3.550017372000      -0.003252572000
       2.852089024000       3.061544408000      -0.005009259000
*H_VDB_BLYP.psp FORMATTED
   LMAX=S
   12
       4.829896620000       1.209449328000      -0.004160981000
       4.874865030000      -1.131837359000       0.003273118000
       3.847285348000      -3.609138791000       0.013924943000
       1.339951403000      -4.589537686000       0.023583475000
      -1.257219301000      -4.591087509000       0.030318008000
      -3.775889801000      -3.630740840000       0.033747037000
      -4.828126595000      -1.209793447000       0.028665970000
      -4.875902354000       1.130204086000       0.021243303000
      -3.843471723000       3.614955577000       0.010554882000
      -1.334243713000       4.588096584000       0.000914849000
       1.257025926000       4.588704910000      -0.005801358000
       3.776400021000       3.629099090000      -0.009234599000
*H_VDB_BLYP.psp FORMATTED
   LMAX=S
   2
       1.216317908000      -0.004972921000       0.009118666000
      -1.218997172000       0.003787130000       0.015400566000
&END
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