[Wien] Questions about difference electron density map

[Ding Peng]

Dear WIEN2k experts,

I am trying to calculate the difference electron density of CeB6, which has a space group of Pm-3m, by WIEN2k (16.04). After I finished running SCF cycles (I used non-magnetic calculation GGA+U calculation, runsp_c_lapw, by forcing the magnetic moment in a spin-polarised setup to zero), I followed the electron density calculation process:

1) check case.scf1, it shows

---------------------------------------------------------------------
 LDA+U potential       added for atom type  1 L=  3 spin up  
:LMAX-WF:   10   Non-Spherical LMAX:   4

          ATOMIC SPHERE DEPENDENT PARAMETERS FOR ATOM  Ce        
:e__0001: OVERALL ENERGY PARAMETER IS    0.5943
          OVERALL BASIS SET ON ATOM IS LAPW
:E2_0001: E( 2)=    0.5943
             APW+lo
:E2_0001: E( 2)=   -6.9944   E(BOTTOM)=   -7.002   E(TOP)=   -6.987  1  2   170
             LOCAL ORBITAL
:E0_0001: E( 0)=    0.5943
             APW+lo
:E0_0001: E( 0)=   -1.8665   E(BOTTOM)=   -2.558   E(TOP)=   -1.175  4  5   176
             LOCAL ORBITAL
:E1_0001: E( 1)=    0.9943
             APW+lo
:E1_0001: E( 1)=   -0.4363   E(BOTTOM)=   -1.448   E(TOP)=    0.575  3  4   197
             LOCAL ORBITAL
:E3_0001: E( 3)=    0.6959   E(BOTTOM)=    0.466   E(TOP)=    0.925  0  1   123
             APW+lo

          ATOMIC SPHERE DEPENDENT PARAMETERS FOR ATOM  B         
:e__0002: OVERALL ENERGY PARAMETER IS    0.5943
          OVERALL BASIS SET ON ATOM IS LAPW
:E0_0002: E( 0)=    0.5943
             APW+lo
:E1_0002: E( 1)=    0.5943
             APW+lo
---------------------------------------------------------------------


2) I choose the default value Emin = -1 and rerun LAPW2 calculation

3) run lstart -sigma to calculate the superposed atomic electron density

4) run lapw5 and set the option "DIFF" in case.in5 




The result difference electron density map was presented by Xcrysden. I found very strong electron accumulation (delta rho is positive) near the core of Ce ions and electron depletion(delta rho is negative) near the core of B ions. 

My questions are:

1) Does this result makes sense?  Because Ce3+ is cation, which should tend to lose electrons, and therefore delta rho should be negative near the core of Ce. This contradicts to my difference electron density map.

2) Is the superposed atomic electron density equivalent to the superposed atomic electron densities from independent atomic model (IAM)? Or it is equivalent to the superposition of the atomic electron densities of ions?

3) Is it correct to set Emin = -1? I had read the past discussions about this topic from the Wien2k email list, but still have no idea how to determine Emin based on the results in case.scf1.


Look forward to the answers.

Many thanks,
Ding