Dear All:
Thanks for your timely reply. I began to understand some mechanism of a NPT CPMD simulation.
However, I am still interested to know the general procedure to start a NPT CPMD simulation.
1. Of course, the first step is always to do a wavefunction optimization.
2. After that I am not sure whether we should start PARRINELLO-RAHMAN NPT immediately [Procedure 1] or control the system temperature first (including TEMPCONTROL IONS step,NOSE IONS step and NOSE ELECTRONS step) followed by pressure control(initiate PARRINELLO-RAHMAN NPT)[Procedure 2]?
3. Following Procedure 2, I tried to initiate PARRINELLO-RAHMAN NPT after controlling the temperature at 1500K for 16 atoms silicon system by NOSE IONS, NOSE ELECTRONS( the second example of day2.pdf tutorial). The input file is shown below:
** INPUT FILE **
******************************************************************************
** &INFO **
** Bulk Silicon. **
** Gamma point calculation with 16 atoms (primitive cell). **
** &END **
** **
** &CPMD **
** MIRROR **
** MOLECULAR DYNAMICS **
** RESTART WAVEFUNCTION COORDINATES CELL **
** RESTART VELOCITIES NOSEP NOSEE **
** EMASS **
** 2000 **
** TIMESTEP **
** 15 **
** NOSE IONS **
** 1500 1500 **
** NOSE ELECTRONS **
** 0.06 10000 **
** MAXSTEP **
** 1000 **
** TRAJECTORY SAMPLE **
** 100 **
** PARRINELLO-RAHMAN NPT **
** SPLINE RANGE **
** 5.0 **
** &END **
** **
** &DFT **
** FUNCTIONAL LDA **
** &END **
** **
** &SYSTEM **
** SYMMETRY **
** FCC **
** SCALE S=2 **
** CELL **
** 20.526204 1.0 1.0 0 0 0 **
** CUTOFF **
** 8.0 **
** PRESSURE **
** 0.0 **
** ISOTROPIC CELL **
** &END **
** **
** &ATOMS **
** *Si_MT_LDA.psp KLEINMAN-BYLANDER **
** LMAX=P **
** 16 **
** 0.00 0.00 0.00 **
** 0.25 0.25 0.25 **
** 1.00 0.00 0.00 **
** 1.25 0.25 0.25 **
** 0.00 1.00 0.00 **
** 0.25 1.25 0.25 **
** 1.00 1.00 0.00 **
** 1.25 1.25 0.25 **
** 0.00 0.00 1.00 **
** 0.25 0.25 1.25 **
** 1.00 0.00 1.00 **
** 1.25 0.25 1.25 **
** 0.00 1.00 1.00 **
** 0.25 1.25 1.25 **
** 1.00 1.00 1.00 **
** 1.25 1.25 1.25 **
** &END **
** **
** &BASIS **
** PSEUDO AO 2 **
** 0 1 **
** &END **
However, even if I increased SPLINE RANGE to 5.0, the warning" SPLINE REGION SMALLER THAN MAXIMUM G-VALUE" is still reported in the output file as shown below:
NFI EKINC EKINH TEMPP EKS ECLASSIC EHAM DIS TCPU
1 1.28022 NaN NaN -84.72569 NaN NaN 0.360E+10 0.09
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
2 NaN NaN NaN NaN NaN NaN NaN 0.08
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
3 NaN NaN NaN NaN NaN NaN NaN 0.09
What is the possible reason for this? Besides that some energy values are shown as "NaN", I don't know why?
4. Adopting Procedure 1, I still got the same problem. The following is my modified input file:
&CPMD
MIRROR
MOLECULAR DYNAMICS
RESTART WAVEFUNCTION COORDINATES CELL
EMASS
400
TIMESTEP
5
TEMPCONTROL IONS
1500 100
MAXSTEP
1000
PARRINELLO-RAHMAN NPT
SPLINE RANGE
5.0
&END
&DFT
FUNCTIONAL LDA
&END
&SYSTEM
SYMMETRY
FCC
SCALE S=2
CELL
20.526204 1.0 1.0 0 0 0
CUTOFF
8.0
PRESSURE
0.0
ISOTROPIC CELL
&END
ATOMS section is ommitted because it is always the same.
Output file also contains the following warnings:
NFI EKINC EKINH TEMPP EKS ECLASSIC EHAM DIS TCPU
1 8.76383 0.00000 1500.0 100.83262 100.93949 109.70332 0.652E-05 0.29
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
2 47.52671 0.00000 1500.0 62.58080 62.68767 110.21438 0.322E-04 0.29
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
3 77.97593 0.00000 1500.0 71.97072 72.07760 150.05353 0.865E-04 0.29
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
4 NaN 0.00000 NaN NaN NaN NaN 0.169E-03 0.29
WARNING| SPLINE REGION SMALLER THAN MAXIMUM G-VALUE
5 NaN 0.00000 NaN NaN NaN NaN NaN 0.30
Does anyone know the possible reason?
Best regards,
Sincerely,
Jun WANG
Department of Chemistry
University of Nebraska-Lincoln
536 Hamilton Hall
Lincoln, NE 68588-0304
U.S.A.
E-mail:junwang at unlserve.unl.edu
junwang at bigred.unl.edu