[Pw_forum] Charge accumulation and depletion

[Giuseppe Mattioli]

Dear Jaret
Yes, I suppose you understood me well...:-)

In the case of US PPs the Bader post-processing does not work well  
because, in my experience at least, the Bader minima may fall into the  
US augmentation charge sphere, so that the values of atomic charge  
become erratic.

Have a nice computation!
Giuseppe

Giuseppe Mattioli
ISM-CNR
Italy

Quoting Jaret Qi <jaretqi at yahoo.com>:

> To make sure I understood you:-case one gives a charge density  
> plot-case two gives a numerical charges difference, right?>>You may  
> also use the external Bader post processing to estimate atomic  
> charges, but it requires (to be reliable) PAW or NC pseudopotentials  
> and hand-adjusted very dense FFT gridsI'm using Ultrasoft PP which  
> means it won't work in my case?
> best-jaretASU
>
>
>      On Friday, October 23, 2015 2:36 AM, Giuseppe Mattioli  
> <giuseppe.mattioli at ism.cnr.it> wrote:
>
>
>
> Dear Jaret
> You may do two (complementary) things:
>
> 1) a Deltarho map. a) Calculation of your whole system and usage of  
> pp.x to extract the charge density (plot_num=0). b) two separate scf  
> calculations
> of the insulator slab and metal slab in the same atomic position of  
> the previous one and usage of pp.x to extract the charge densities.  
> c) Subtract
> the charge densities calculated in b) to the charge densities  
> calculated in a). If you open the obtained file with xcrysden you  
> can visualize the
> charge displacement at the interface (menu tools --> data grid).
>
> Something like this, which has been set up for a molecule/surface system...
>
> export FILEA="molecule+surface"
> export INPFILE=$FILEA-cha.inp
> export OUTFILE=$FILEA-cha.out
> echo " $FILEA"
> echo " $INPFILE"
> echo " $OUTFILE"
> cat > $INPFILE << EOF
>  &inputpp
>     prefix  = '$FILEA'
>     outdir = '$TMP_DIR/'
>     filplot = '$FILEA-cha.dat'
>     plot_num= 0
>  /
> EOF
> $PARA_PREFIX $ESPRESSO/pp.x $PARA_POSTFIX < $INPFILE >> $OUTFILE
>
> export FILEB="molecule"
> export INPFILE=$FILEB-cha.inp
> export OUTFILE=$FILEB-cha.out
> echo " $FILEB"
> echo " $INPFILE"
> echo " $OUTFILE"
> cat > $INPFILE << EOF
>  &inputpp
>     prefix  = '$FILEB'
>     outdir = '$TMP_DIR/'
>     filplot = '$FILEB-cha.dat'
>     plot_num= 0
>  /
> EOF
> $PARA_PREFIX $ESPRESSO/pp.x $PARA_POSTFIX < $INPFILE >> $OUTFILE
>
>
> export FILEC="surface"
> export INPFILE=$FILEC-cha.inp
> export OUTFILE=$FILEC-cha.out
> echo " $FILEC"
> echo " $INPFILE"
> echo " $OUTFILE"
> cat > $INPFILE << EOF
>  &inputpp
>     prefix  = '$FILEC'
>     outdir = '$TMP_DIR/'
>     filplot = '$FILEC-cha.dat'
>     plot_num= 0
>  /
> EOF
> $PARA_PREFIX $ESPRESSO/pp.x $PARA_POSTFIX < $INPFILE >> $OUTFILE
>
> export FILE="rho-int-$FILEA"
> export INPFILE=$FILE.inp
> export OUTFILE=$FILE.out
> echo " $FILE"
> echo " $INPFILE"
> echo " $OUTFILE"
> cat > $INPFILE << EOF
>  &inputpp
>  /
>  &plot
>     nfile = 3
>     filepp(1) = '$FILEA-cha.dat'
>     weight(1) = 1.0
>     filepp(2) = '$FILEB-cha.dat'
>     weight(2) = -1.0
>     filepp(3) = '$FILEC-cha.dat'
>     weight(3) = -1.0
>     iflag = 3
>     output_format = 5
>     fileout = '$FILE.plot'
>     e1(1) =1.0, e1(2)=1.0, e1(3) = 0.0,
>     e2(1) =0.0, e2(2)=0.0, e2(3) = 1.0,
>     nx=56, ny=40
>  /
> EOF
> $PARA_PREFIX $ESPRESSO/pp.x $PARA_POSTFIX < $INPFILE >> $OUTFILE
>
> 2) Use projwfc.x to obtain (Lowdin) atomic charges of your whole  
> system and of the separate slabs (you may also relax the slabs, in  
> this case, to
> account for surface effects). Then you compare the atomic charges to  
> look for charge displacement. Be aware that there is a spilling  
> parameter at the
> end of the projwfc output which indicates how much of your charge  
> density does not fit into the Lowding atomic partitioning. Your  
> results are
> reasonably meaningful only if the spilling parameter is similar for  
> all your calculations... You may also use the external Bader post  
> processing to
> estimate atomic charges, but it requires (to be reliable) PAW or NC  
> pseudopotentials and hand-adjusted very dense FFT grids. You may  
> like to have a
> look here if you want to try
>
> http://theory.cm.utexas.edu/henkelman/code/bader/
>
> HTH
> Giuseppe
>
> On Friday, October 23, 2015 06:12:17 AM you wrote:
>> Dear Giuseppe,My system is an interface between an insulator and half-metal.
>> -Jaret
>> AST, USA>Dear mahmoudASU
>>
>> >First of all sign always your posts to this Forum with name and  
>> affiliation, please.
>> >
>> >There are many ways to calculate charge displacements (Deltarho  
>> plots, atomic charge calculations, ...), but their best usage  
>> depends on >the kind
>> >of  charge displacement occurring in your system (molecule-surface  
>> interaction, charge transfer affecting dopants or defects in a  
>> >semiconductor
>> >matrix, ...). Impossible to say more without knowing more...
>> >
>> >HTH
>> >
>> >Giuseppe 
>> >
>> >On Wednesday, October 21, 2015 11:42:37 PM Jaret Qi wrote:
>> >> Hello QE users,Is there a way to calculate Charge accumulation  
>> and depletion in quantum espresso, if so then how?
>> >> -mahmoudASU
>
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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), Italy   
>   Tel + 39 06 90672836 - Fax +39 06 90672316   
>   E-mail: <giuseppe.mattioli at ism.cnr.it>
>   http://www.ism.cnr.it/english/staff/mattiolig
>   ResearcherID: F-6308-2012


-- 
********************************************************
- Article premier - Les hommes naissent et demeurent
libres et ègaux en droits. Les distinctions sociales
ne peuvent être fondèes que sur l'utilitè commune
- Article 2 - Le but de toute association politique
est la conservation des droits naturels et
imprescriptibles de l'homme. Ces droits sont la libertè,
la propriètè, la sùretè et la rèsistance à l'oppression.
********************************************************

    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>