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

[huawj]

Hi Axel and  Eduard,

	Thank you for your replies. I mistook the real meaning of 'quench' once. 
'QUENCH BO ELECTRONS' is only  done at the starting configuration( NFI=0),
and its purpose is to set the velocities of electrons  zero and then to optimize 
the wavefunctions. And I have lerant to adjust the convergence creteria to 
'quench to the BO surface' in not too long steps.
(I found the 'proton transfer in water' in Dr. Axel's homepage is very useful for 
beginners. I have benefitted a lot.)

 I changed all the hydrogens into deuteriums, thus it would be resonable to use such
 a large timestep.


All the best,
Weijie 





======= 2006-10-05 00:02:39 you wrote£º=======

>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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>>
>>
>
>
>-- 
>=======================================================================
>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.
>

= = = = = = = = = = = = = = = = = = = =

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
2006-10-05