[Pw_forum] reusing wfc/charge density for nscf calculation with different total charge

[Giuseppe Mattioli]

Dear Alexey
I did not follow the whole thread, but I was looking at your latest  
input files, and I was wondering whether the options below might do  
the trick...

  &control
     calculation = 'scf'
     restart_mode='from_scratch'
     ...
  /

  &electrons
     ...
     startingpot = 'file'
     startingwfc = 'file'
  /

They should allow you for restarting from wfc and potential calculated  
at the end of the scf. I always used them to perform a scf run (with  
Hubbard alpha, you know...) after a previous scf run. I do not know if  
you can start a nscf calculation from scratch, but a scf calculation  
with the above constraint may be useful to your purpose...
HTH
Giuseppe

Giuseppe Mattioli
ISM-CNR
Italy

Quoting Alexey Akimov <aakimov_guest at z.rochester.edu>:

> Dear Paolo,
>
> First of all, thank you for your reply - i though that my message  
> haven't got to the forum.  Yes, you are right - if i set the same  
> tot_charge for nscf calculation as that for scf - everything works  
> fine. But the idea is to use different charges for nscf (+0.25) and  
> scf (0.0) calculations, and at the same time use the same  
> wavefunction (obtained from the scf calculation). So when i try to  
> do that, i get the errors below. I think this is because one is not  
> supposed to do this kind of trick, normally. So would it be possible  
> to do this without digging much into the code and rather using more  
> standard options?
>
> CRASH:
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>    
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      task #         0
>      from potinit : error #         1
>      starting and expected charges differ
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
>
> portion of the nscf output (i run on several CPUs):
>
>      The potential is recalculated from file :
>      ./x.save/charge-density.dat
>
>
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine potinit (1):
>      starting and expected charges differ
>      Error in routine potinit (1):
>      starting and expected charges differ
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
>      stopping ...
>
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine potinit (1):
>   
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
>      stopping ...
>
>
>
>
> Below are the relevant portions of the scf and nscf input files:
>
> SCF input:
>
> &CONTROL
>   calculation = 'scf',
>   pseudo_dir = <my path>
>   outdir = './',
>   prefix = 'x',
> /
>
> &SYSTEM
>   ibrav = 0,
>   celldm(1) = 1.89,
>   nat = 6,
>   ntyp = 1,
>   nbnd = 50,
>   tot_charge = 0.25,
>   occupations = 'smearing',
>   starting_magnetization(1) = 0.0,
>   smearing = 'gaussian',
>   degauss = 0.005,
>   ecutwfc = 40,
>   ecutrho = 400,
>   nspin = 2,
>   nosym = .true.,
> /
>
>
> NSCF input:
>
> &CONTROL
>   calculation = 'nscf',
>   pseudo_dir = <my path>
>   outdir = './',
>   prefix = 'x',
> /
>
> &SYSTEM
>   ibrav = 0,
>   celldm(1) = 1.89,
>   nat = 6,
>   ntyp = 1,
>   nbnd = 50,
>   tot_charge = 0.0,
>   starting_magnetization(1) = 0.0,
>   occupations = 'smearing',
>   smearing = 'gaussian',
>   degauss = 0.005,
>   ecutwfc = 40,
>   ecutrho = 400,
>   nspin = 2,
>   nosym = .true.,
> /
>
>
>
>
>
> ----- Original Message -----
> From: "Paolo Giannozzi" <paolo.giannozzi at uniud.it>
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Sent: Thursday, May 30, 2013 4:59:18 AM
> Subject: Re: [Pw_forum] reusing wfc/charge density for nscf  
> calculation with different total charge
>
> On Tue, 2013-05-21 at 21:34 -0400, Alexey Akimov wrote:
>
>> when PW (with the input for nscf calculations for neutral system)
>> tries to read the wavefunction/charge density for the charged system
>> it crashes, because the expected charge is different from the one
>> deduced from the wfc files
>
> I am not sure but if you set a charge (tot_charge) for the nscf as well,
> the calculation should succeed. Note that nothing changes in the nscf
> if you set a nonzero charge: only occupancies should change, not
> eigenvalues, since these depend only upon the potential
>
> P.
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
> --
> Dr. Alexey V. Akimov
>
> Postdoctoral Research Associate
> Department of Chemistry
> University of Rochester
>
> aakimov_guest at z.rochester.edu
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum


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    Giuseppe Mattioli
    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
    v. Salaria Km 29,300 - C.P. 10
    I 00015 - Monterotondo Stazione (RM)
    Tel + 39 06 90672836 - Fax +39 06 90672316
    E-mail: <giuseppe.mattioli at ism.cnr.it>