[Wien] in1new problem

[Stefaan Cottenier]

Dear all,

I observe a problem when using in1new, and I'm not sure whether this is 
due to my misunderstanding or due to a problem with the method:

The compound is LaSb in the NaCl structure, using spin-orbit coupling. 
If in1new is used (eseper0=0.40 is needed), the scf-cycle stops with the 
famous QTL-B error, in a band with energy close to -6 Ry. There are two 
states with such an energy: La-4d and Sb-4p. These are the corresponding 
eigenvalues at gamma, without and with spin-orbit:

no spin-orbit :
       EIGENVALUES ARE:
        -6.0760613   -6.0760009   -6.0759824   -5.9252884   -5.9252770
        -5.9252356   -5.9248027   -5.9247402

with spin-orbit :
     EIGENVALUES ARE:
          -6.4754331   -6.4754331   -6.0550927   -6.0550927   -6.0550443
          -6.0550443   -5.8783683   -5.8783683   -5.8783219   -5.8783219
          -5.8389144   -5.8389144   -5.8386363   -5.8386363   -5.8385865
          -5.8385865

If the old linearization scheme is used, acceptable energies are found:

La-4d:
          E( 2)=   -5.9275   E(BOTTOM)=   -5.930   E(TOP)=   -5.925

Sb-5p:
          E( 1)=   -6.0800   E(BOTTOM)=   -6.090   E(TOP)=   -6.070  

However, in1new finds quite different values:

La-4d: -5.9193, which is quite correct :

:QTL001: 1.9855 5.268411.0825 0.1647 1.7559 3.5126 0.0000 2.2848 2.2855 
2.1701 4.3420 0.0000
        Q-s-low E-s-low   Q-p-low E-p-low   Q-d-low E-d-low   Q-f-low 
E-f-low
:EPL001:  1.8705 -1.2546    4.5593 -0.1360   10.0095 -5.9193    0.0057 
-0.6566

Sb-5p: -5.9529, which seems too low to me. Note also the 6.126 p-electrons.

:QTL002: 1.2628 7.706610.0104 0.0443 2.5679 5.1387 0.0000 2.0061 2.0061 
1.9993 3.9989 0.0000
        Q-s-low E-s-low   Q-p-low E-p-low   Q-d-low E-d-low   Q-f-low 
E-f-low
:EPL002:  0.2081 -0.2120    6.1269 -5.9529    9.9223 -1.0701    0.0154 
-0.2356

A calculation using the old linearization scheme converges smoothly, 
when the in1new is used (even when starting from the converged case), 
then a QTL-B error shows up almost immediately.

If no spin-orbit coupling is used, then convergence is much better even 
with in1new (still hindered by a QTL-B of about three at the fermi 
energy). Now, in1new identifies the correct energies:

La :

:QTL001: 1.9856 5.267911.0853 0.1653 1.7554 3.5125 0.0000 2.2862 2.2870 
2.1701 $
        Q-s-low E-s-low   Q-p-low E-p-low   Q-d-low E-d-low   Q-f-low 
E-f-low
:EPL001:  1.8625 -1.2606    0.0147 -1.0864   10.0033 -5.9217    0.0029 
-1.1257

Sb (note also the Q-p, which is much closer to 6.0 now) :

:QTL002: 1.2637 7.707210.0091 0.0442 2.5677 5.1395 0.0000 2.0059 2.0059 
1.9990 $
        Q-s-low E-s-low   Q-p-low E-p-low   Q-d-low E-d-low   Q-f-low 
E-f-low
:EPL002:  0.0061 -1.2675    6.0049 -6.0659    9.8659 -1.0725    0.0016 
-1.2955

My hypothesis is that in1new is not able to deal with the large 
spin-orbit splitting in the Sb-4d. I'm not sure whether this is 
connected by the presence of La states at nearly the same energy or not.

Is this analysis correct? And how can this problem be circumvented? I 
wanted to use in1new in this case because I want to cover a broad volume 
range, over which the Fermi energy changes a lot. I can of course put 
proper energies by hand for every volume, but that's just what in1new 
was designed for to avoid...

Thanks,
Stefaan