The partial charge density (1)

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The partial charge density corresponding to the band structure(QuantumWise Forum)

Dear users

how could i calculate the partial charge density corresponding to the certain band in band structure.

 

zh:The concept of the partial charge density of a given band or eigenvalue is basically the same as the local density of states.

The summing up the the local density of states for the eigenvalues at a specified band will give the band-decomposed partial charge density.

 

caocao:thanks for your kind reply, could i make the input file by using VNL?

if i want to calculate the partial charge density corresponding to the defect state in band structure,

how can i know the  Eigenstate of this defect state?

 

zh: At first, you should know the band index of the defect state under study

 

caocao:

and what is the different between the isosurface of certain eigenstate and the partial charge density corresponding to certain band in band structure

 

zh: Actually, the partial charge density is the squared eigenstate for a given k and eigenvalue. 

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"Partial charge density"  (ABINIT Discussion Forums)

Dear all
is it possible to calculate the partial charge density on specific band and k-point with Abinit?
Cheers.

 

Hi!

For bands you just use "occ" variable, when it comes to printing, to occupy the wanted band and leave the other bands unoccupied (put occ to zero for them).

For k points I'm not sure.

Best regards,

Igor L.

 

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“Band decomposed charge with in an atomic volume” (UT theoretical chemistry code forum)

Dear all,

As implemented in VASP, we can calculate band decomposed charge density, a PARCHG file,

which is originated from given wave functions.

 

Can the bader code calculate band decomposed charge within atomic volume by combining

the PARCHG file and atomic volumes from bader analysis ?

Thank you in advance for your kind response,

Kuwabara

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Vasp.4.4 can calculate the partial (band decomposed) charge density according to parameters specified in the file INCAR.

Mind that the partial charge density can be calculated only if a preconverged WAVECAR file exists, vasp enters the evaluation routine very quickly and stops immediately after evaluating the partial charge density. This implementation was chose to allow a fast (almost interactive) recalculation of the charge density for particular bands and kpoints.

The following parameters control the behavior of VASP.

• LPARD: Evaluate partial (band and/or k-point) decomposed charge density. We want to stress again, that the wavefunctions read from WAVECAR must be converged in a separate prior run.
• There are several ways how to specify for which bands the charge density is evaluated: In general the input lines with IBAND, EINT and NBMOD control this respect of the routine:
• IBAND: Calculate the partial charge density for all bands specified in the array IBAND. If IBAND is specified in the INCAR file and NBMOD is not given, NBMOD is set automatically to the size of the array. If IBAND is for instance

               IBAND= 20 21 22 23

  the charge density will be calculated for bands 20 to 23.

• EINT: Specifies the energy range of the bands that are used for the evaluation of the partial charge density. Two real values should be given, if only one value is specified, the second one is set to . If EINT is given and NBMOD is not specified, NBMOD is set automatically to -2.
• NBMOD: This integer variable can take the following values

  >0  Number of values in the array IBAND. If IBAND is specified, NBMOD is set automatically to the correct value (in that case NBMOD should not be set manually in the INCAR file)

    0  Take all bands to calculate the charge density, even unoccupied bands are taken into account.

   -1  Calculate the total charge density as usual. This is the default value if nothing else is given.

   -2  Calculate the partial charge density for electrons with there eigenvalues in the range specified by EINT.

   -3  The same as before, but the energy range is given vs. the Fermi energy.

   

• KPUSE: KPUSE specifies which k-points are used in the evaluation of the partial dos. KPUSE is an array of integer values.

           KPUSE= 1 2 3 4

  means that the charge density is evaluated and summed for the first four k-points. Be careful: VASP changes the kpoint weights if KPUSE is specified.

• LSEPB: Specifies whether the charge density is calculated for every band separately and writen to a file PARCHG.nb. (TRUE) or whether charge density is merged for all selected bands and write to the file PARCHG.ALLB. or PARCHG. Default is FALSE.
• LSEPK: Specifies whether the charge density of every k-point is write to the files PARCHG. .nk (TRUE) or whether it is merged (FALSE) to a single file. If the merged file is written, then the weight of each k-point is determined from the KPOINTS file, otherwise the kpoints weights of one are chosen.

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References:

[1]  Questions and Answers: http://quantumwise.com/forum/index.php?topic=1356.0;wap2 ;

      http://quantumwise.com/forum/index.php?topic=1356.msg6656#msg6656

[2] The meeting place for ABINIT users and developers: http://forum.abinit.org/viewtopic.php?f=9&t=2568

[3] LocalDeviceDensityOfStates: 

     http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.localdevicedensityofstates.html

[4] http://theory.cm.utexas.edu/forum/viewtopic.php?f=1&t=1554

[5] http://cms.mpi.univie.ac.at/vasp/guide/node145.html