[Pw_forum] Help me to solve a problem in Charge Density Difference calculation using Quantum Espresso

stefano de gironcoli degironc at sissa.it
Sat Aug 12 17:08:19 CEST 2017


you take the final vc-relaxed cell and assume the same for the two 
separate fragments.
And you need to redo the scf calculation (only the scf calculation) of 
the combined system so as to have the same parameters for all three.

stefano



On 12/08/2017 17:04, Bibhas Manna wrote:
> Dear Matthieu,
>
> Since, I have done the geometry relaxation using *vc-relax,* how can I 
> maintain the same *Cell_Parameters* for all the three cases.
>
> Thanks.
> Bibhas
>
>
> On Sat, Aug 12, 2017 at 8:22 PM, Matthieu Fortin-Deschênes 
> <matthieu.fortin-deschenes at polymtl.ca 
> <mailto:matthieu.fortin-deschenes at polymtl.ca>> wrote:
>
>     I'm no expert, but I think you need to make the scf calculations with
>     the same parameters, especially ecutrho and CELL_PARAMETERS.
>
>     Matthieu
>
>     Bibhas Manna <mannabibhas at gmail.com
>     <mailto:mannabibhas at gmail.com>> a écrit :
>
>     > Dear Sir,
>     >
>     > Thanking you for your quick reply.
>     >
>     > I have used the same parameter for three charges. Following are
>     the input
>     > pp.x files:
>     >
>     >
>     > *For Substrate + molecules:*&inputpp
>     >     prefix  = 'PG_4_HCHO_PBE'
>     >     outdir = './tmp/'
>     >     filplot = 'PG_4_HCHO_charge'
>     >     plot_num= 0
>     >  /
>     >  &plot
>     >     nfile = 1
>     >     filepp(1) = 'PG_4_HCHO_charge'
>     >     weight(1) = 1.0
>     >     iflag = 2
>     >     output_format = 3
>     >     fileout = 'PG4_HCHO.rho.dat'
>     >     e1(1) =1.0, e1(2)=0, e1(3) = 0.0,
>     >     e2(1) =0.0, e2(2)=0.0, e2(3) = 1.0,
>     >     nx=56, ny=40
>     >  /
>     >
>     > *For Substrate only:*&inputpp
>     >     prefix  = 'PG_4_PBE'
>     >     outdir = './tmp/'
>     >     filplot = 'PG_4_charge'
>     >     plot_num= 0
>     >  /
>     >  &plot
>     >     nfile = 1
>     >     filepp(1) = 'PG_4_charge'
>     >     weight(1) = 1.0
>     >     iflag = 2
>     >     output_format = 3
>     >     fileout = 'PG4.rho.dat'
>     >     e1(1) =1.0, e1(2)=0.0, e1(3) = 0.0,
>     >     e2(1) =0.0, e2(2)=0.0, e2(3) = 1.0,
>     >     nx=56, ny=40,
>     >  /
>     >
>     >
>     > *For Gas molecule only:*&inputpp
>     >     prefix  = 'HCHO_PBE'
>     >     outdir = './tmp/'
>     >     filplot = 'HCHO_charge'
>     >     plot_num= 0
>     >  /
>     >  &plot
>     >     nfile = 1
>     >     filepp(1) = 'HCHO_charge'
>     >     weight(1) = 1.0
>     >     iflag = 2
>     >     output_format = 3
>     >     fileout = 'HCHO.rho.dat'
>     >     e1(1) =1.0, e1(2)=0.0, e1(3) = 0.0,
>     >     e2(1) =0.0, e2(2)=0.0, e2(3) = 1.0,
>     >      nx=56, ny=40,
>     > /
>     >  I am actually getting  error in the reading of the filepp(2) as
>     follows:
>     >
>     > Reading header from file  PG_4_HCHO_charge
>     >
>     >    Info: using nr1, nr2, nr3 values from input
>     >      Reading data from file  PG_4_HCHO_charge
>     >      Reading data from file  PG_4_charge
>     >
>     >
>     >
>     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>     >      Error in routine chdens (1):
>     >      incompatible gcutm or dual or ecut
>     >
>     >
>     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>     >
>     >      stopping ...
>     >
>     > Thanks.
>     > Bibhas
>     >
>     > On Sat, Aug 12, 2017 at 7:59 PM, stefano de gironcoli
>     <degironc at sissa.it <mailto:degironc at sissa.it>>
>     > wrote:
>     >
>     >> you need to compute the three charges with the same parameters
>     >>
>     >> stefano
>     >>
>     >>
>     >> On 12/08/2017 16:20, Bibhas Manna wrote:
>     >>
>     >> Dear All,
>     >>
>     >> I am very new to Quantum Espresso. I want to get a charge density
>     >> difference plot for a gas molecule adsorbed on the single layer
>     graphene
>     >> surface. Presently I am using pp.x to compute the same in QE v.5.1
>     >> following an equation:
>     >>
>     >>     ∆ρ=ρAB – ρA-ρB
>     >>
>     >> Where, ρAB, ρA and ρB are the charge densities of graphene
>     -molecule
>     >> complex, graphene and molecule respectively. I have
>     successfully computed
>     >> all of these three charge densities using pp.x. Now, I am
>     trying to find
>     >> out the charge density difference using pp.x with nfile = 3,
>     while all of
>     >> these three charge files are available to me as inputs.
>     >>
>     >> Unfortunately, I got an error in the output log:
>     >> *Error in routine chdens (1):
>     >>        incompatible gcutm or dual or ecut*
>     >>
>     >> Since, I have different number of atoms in each of the three
>     files, how
>     >> can I make the charge files having same number of atomic
>     coordinates?
>     >>
>     >> I am sharing my input and output files for your kind
>     considerations.
>     >>
>     >> Can you help me to solve this problem?
>     >>
>     >> Thanks with regards,
>     >> Bibhas Manna
>     >> Research Scholar,
>     >> IIT Kharagpur, India
>     >>
>     >>
>     >>
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