[CPMD-list] Troubles testing GaAs

[Eyvaz Isaev]

Dear all,

I am testing GaAs and, surprisingly, met some
troubles.

There are encountered problems:

1. Lanczos + Vanderbilt PsP combination gives an
enormous error for
B2MIN and B2MAX.


****************************************************************
 *   ATOM       MASS   RAGGIO NLCC             
PSEUDOPOTENTIAL *
 *    Ga     69.7200   1.2000  YES             
VANDERBILT      *
 *    As     74.9220   1.2000  YES             
VANDERBILT      *

****************************************************************

EWALD SUM absent!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 <<<<<<<<<<<<<<<<<<< LANCZOS DIAGONALIZATION
<<<<<<<<<<<<<<<<<<<<
 >> CYCLE     NCONV        B2MAX        B2MIN    
#HPSI      TIME
        1         0    3.487E+42    1.000E+30     
8.00      9.24
        2         0    4.115E+42    4.822E+18     
7.00      9.14
        3         0    2.992E+40    3.309E+12     
7.00      9.11

By the way it may be caused due to an error about
Ewald sum.
I have no idea why Ewald sum absents.

2. Vanderbilt type PsP is not compatible with
Monkhorst-Pack k-points:

PROGRAM STOPS IN SUBROUTINE SETSYS| K-POINTS WITH
VANDERBILT NOT IMPLEMENTED

3. Test using ODIIS method and Vanderbilt type PsP
seems never will be converged.

 ODIIS| Insufficient progress; reset!
5747  3.812E-01   7.778E-02    -725.679718  
-3.155E+01      5.28
5748  1.264E+00   2.356E-01    -652.074943   
7.360E+01      5.31
5749  6.561E-01   5.359E-02    -735.670382  
-8.360E+01      5.40
5750  1.181E+00   8.692E-02    -714.601328   
2.107E+01      5.49

In this case only \Gamma point is applied, isn't it?

4. I am not sure that results I found are good when
Goedecker type PsP
is applied.

a) Energy via lattice parameter is strange (it seems
there are 2 minima).

5.65 (B+E2+X-V) TOTAL ENERGY = -245.03314131 A.U.
5.66 (B+E2+X-V) TOTAL ENERGY = -244.97934288 A.U.
5.67 (B+E2+X-V) TOTAL ENERGY = -245.00667290 A.U.
5.68 (B+E2+X-V) TOTAL ENERGY = -245.00457030 A.U.
5.69 (B+E2+X-V) TOTAL ENERGY = -245.00533431 A.U.
5.70 (B+E2+X-V) TOTAL ENERGY = -244.94863815 A.U.

Of course, it may be connected with convergence
problem (may be cutoff energy
36 Ry is not sufficient for 3d-electrons in Ga).

b) Besides occupance numbers are strange: I have
exactly 36 filled bands for
8 atoms in the cubic cell (13*4+ 5*4), but for k-point
3/4,3/4,3/4
even 37-th band is filled.

 K POINT:       1    0.375000    0.375000    0.375000 
  0.125000

    35      2.9491468     2.000       36     
3.0419036     2.000
    37      3.0419036     2.000       38     
3.9066380     0.000

 K POINT:       2    0.375000    0.375000    0.125000 
  0.375000

    35      2.7371278     2.000       36     
3.3659589     2.000
    37      3.8350205     0.000       38     
4.6426493     0.000

 K POINT:       3    0.375000    0.125000    0.125000 
  0.375000

    35      3.0925761     2.000       36     
3.1181842     2.000
    37      4.1882453     0.000       38     
4.9720836     0.000

 K POINT:       4    0.125000    0.125000    0.125000 
  0.125000

    35      3.5761476     2.000       36     
3.6583125     0.000
    37      3.6583125     0.000       38     
5.4236853     0.000

I have attached my input files. Maybe something is
wrong there.
Hope somebody will be able to correct me.

Sorry for a rather long mail.

Regards,
Eyvaz Isaev

Theoretical Physics Department
Moscow Steel and Alloys Institute


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