[CPMD-list] question on the QUENCH[IONS, ELECTRONS, CELL, BO] keyword

[Axel Kohlmeyer]

On 10/4/06, huawj <huawj at itcc.nju.edu.cn> wrote:
> Dear All，
>
> I tried the keyword
>          QUENCH BO ELECTRON
> for a (31H2O +HCl) system at 300K(which started from a equilibrated configuration using classical MD and relaxed for 1 ps using CPMD),
> but get confused about the following questions:
>
> (1)  From the cpmd-manual, I can read the illustrations for this keyword:
> "The velocities of the ions, wavefunctions or the cell are set to _zero_ at the beginning of the run.
> With the option BO the wavefunctions are converged at the beginning of the MD run.  "
>
> But why here the resulting EKINC of the first step is not _zero_ , but a positive value instead ?
>
>        NFI    EKINC   TEMPP           EKS      ECLASSIC          EHAM         DIS    TCPU
>          1  0.00040   302.0    -490.88033    -490.74549    -490.74509   0.486E-04    8.31

because this is the first MD step _after_ the quench, i.e. your
electrons are moving again.

>          2  0.00362   285.0    -490.87575    -490.74849    -490.74487   0.189E-03    8.34
>          3  0.01012   300.0    -490.87335    -490.73940    -490.72928   0.412E-03    8.32
>          4  0.01866   280.9    -490.87342    -490.74801    -490.72935   0.727E-03    8.33
>          5  0.02698   300.0    -490.87535    -490.74140    -490.71442   0.112E-02    8.34
>            ......
>         48  0.02502   315.3    -490.88021    -490.73946    -490.71443   0.959E-01    9.44
>         49  0.02513   316.6    -490.88090    -490.73955    -490.71443   0.995E-01    9.39
>         50  0.02529   317.8    -490.88163    -490.73972    -490.71443   0.103E+00    9.45
>
>
>
> (2) Why the "quench to the BO surface" step should not take more than 50 steps ?

please provide a reference for that. this may depend a lot on context.
how fast a wavefunction converges depends on your specific setup.

> (3) In the case the running takes more than 50 steps, I adjusted the convergence parameter (CONVERGENCE ORBITALS 2.0E-5), but nothing changed in the output file. Even no statement about the convergence creteria can be found in the output file. Why can this happen?
>

please check your outputs more carefully. convergence parameters are echoed.

axel.


> (4) Suppose I have converged the wavefunctions with the creteria  2.0E-5 in less than 50 steps, is there anything else should I do before
> I start a simulation of trajectory using a Nose-Hoover chain thermostat? Should I reoptimize the wavefunction to get a much higher convergence creteria, e.g. 1.0E-6 ?
>
> Thank you very much.
>
> ==input file for quenching the electrons to the BO surface======
>
> &CPMD
> MOLECULAR DYNAMICS CP
> RESTART WAVEFUNCTION  COORDINATES VELOCITIES
> QUENCH BO ELECTRONS
> TRAJECTORY XYZ
> TEMPERATURE
>  300.0
> TEMPCONTROL IONS
>  300.0 30.0
> TIMESTEP
> 7.0
> MAXSTEP
> 50
> EMASS
> 1000.0
> MEMORY BIG
> &END
>
>
>
>
>
>
>
>
> Best regards,
>
> Weijie Hua
> Institute of Theoretical and Computational Chemistry,
> Key Laboratory of Mesoscopic Chemistry,
> School of Chemistry and Chemical Engineering,
> Nanjing University,Nanjing 210093,
> P.R.China
> Email:huawj at itcc.nju.edu.cn
> 2006-10-04
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>
>


-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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