[xcrysden] About isovalue

[Yamit]

Dear Prof. Scott Beckman

Thank you for the enlightenment !!

About selection of isovalue:

I would like to know, if I have to compare two systems (say, Si and Ge), which iso-value should I select for both of them? (so that comparison is valid.)

Thank you once again!!!

Thanks & Regards
Amit


On Mon, 02 Aug 2010 18:11:00 +0530  wrote
>


The charge is not calculated at EFermi, but it is the sum of the charge
from the Kohn-Sham states integrated over the Brillouin zone and summed
from the lowest state to the EFermi.  



The integral over the
charge distribution (on your XSF grid) should equal "nelec" from PWSCF. 




The minimum and maximum value tells you the min. and max. value on the
XSF grid.  So if you have a uniform charge concentration min=max.  For
Si it is likely that 0.0014 will be located somewhere in an
interstitial region and 0.87 will be located in a bond-charge.  



I wouldn't say that there is any "ideal" isovalue.  I would fiddle with
this value and look at the charge distribution.  This will allow you to
develop qualitative picture of how your system works.  











Yamit wrote:
Hello All

  

I am using Xcrysden to plot charge density of Silicon (example 05:
Quantum Esspresso-4.2). 

*) Could anyone please tell the details of "xsf" file?

( This charge density is calculated at Fermi Energy. Please also
correct me, if I am wrong.)

  

*)When for Silicon: Minimum grid value :0.001411 and 

Maximum grid value : 0.87371

What should be the ideal isovalue? Are there any rules to select the
isovalues, from the values in *.xsf file? 

  

(For isovalue of 0.001411(min) & 0.87371(max), no charge density
has been found. )

  

Thank you in advance!!!

  

Regards

Amit N. Harode

CRL INDIA

  

P.S.

Input file for QE's pp.x is as follows, &inputpp

prefix = 'si'

filplot = 'sicharge'

plot_num= 0

/

&plot

nfile = 1

filepp(1) = 'sicharge'

weight(1) = 1.0

iflag = 3

output_format = 5

fileout = 'si.rho.xsf'

/

  

  
    
      
        
      
    
  
  

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