[CPMD-list] Energy conservation etc.

[padma at uiuc.edu]

Dear cpmd users, 

  I am facing poor energy conservation in CPMD runs of a 
CO2+ water system (one CO2 molecule in 46 H2O) with PBC. 
(The input file used for the MD is given below.)
The starting configuration was force-field-equilibrated
structure of the system which is then wavefunction optimized
to 10.0d-6. 

The conservation (slope) of EHAM over a 5 ps run was 
about 10d-4/ps (which, I believe, is atleast one order
poorer than acceptable value). The kinetic energy of electrons 
and ions looked pretty good with fluctuations about their 
set-values.  

Further, hoping that some adjustments in the input parameters 
would improve the situation, a shoter run of about 0.2 ps 
is made (starting from the RESTART file at the end of 
the 5ps run) with the following options:  
  
RESTART LATEST WAVEFUNCTION COORDINATES VELOCITIES NOSEP 

QUENCH BO 

NOSE IONS
    300.0  3200.0
nose electrons
    0.02  10000.0

(no MASSIVE thermostating for ions and no thermostating 
at all for the electrons)

also in &DFT section the GC-CUTOFF increased

  GC-CUTOFF
    1.0e-5

But KSH was found greater then EHAM  during the whole run!! 
And the NOSE ENERGY IONS  listed in the AVERAGED QUATITIES at
the end of the run was negative (~ -0.9 ).              

I would be very greatful to know what's going wrong 
and how can I improve the conservation. 

best regards,
Padma


&CPMD
  MOLECULAR DYNAMICS CP
  optimizE WAVEFUNCTION
  RESTART LATEST WAVEFUNCTION COORDINATES VELOCITIES NOSEP NOSEE
  CONVERGENCE
    1.0e-6  1.0e-6
  SPLINE POINTS
    1001
  TEMPERATURE
    300.0
  NOSE IONS MASSIVE
    300.0  2500.0
  NOSE ELECTRONS
    0.02  10000.0
  MAXSTEP
    4000
  TRAJECTORY SAMPLE
    20
  TIMESTEP
    4.0
  EMASS
    600.0
&END
                                   
&DFT
  NEWCODE
  EXCHANGE CORRELATION TABLE NO
  FUNCTIONAL BLYP
  GC-CUTOFF
    5.0e-6
&END

&SYSTEM
  ANGSTROM
  SYMMETRY
    1
  CHARGE
    0.0
  CELL
11.3 1.0 1.0 0.0 0.0 0.0
  CUTOFF
    25.0
&END
                                                             
                                    
&ATOMS
                                                             
*C_VDB_BLYP.psp NEWF FORMATTED 
LMAX=P  
 1

[COORDINATES ]

*O_VDB_BLYP.psp NEWF FORMATTED
   LMAX=P
   48

[ COORDINATES ]

*H_VDB_BLYP.psp NEWF FORMATTED
   LMAX=S
   92

[ COORDINATES ]

&END