[Pw_forum] wrong result from converted abinit LDA FHI PP

[James Mao]

Dear all,

I learned how to generate and test PPs in the past several days, and 
generated NC-LDA PPs for oxygen and carbon using PSLibrary code for 
practice. They were tested using ld1.x first, then a CO2 vibrational 
run to compare with results from known pbe-rrkjus PPs, as well as all 
electrons results. Everything looks fine.

I also converted fhi PP from Abinit and tested them. The results of 
ld1 test looks fine: e(eigen) of AE-PS and \delta E are small,  wfc 
and logarithmic derivative match AE results. However, the results of 
CO2 vibrational calculations using these converted PPs are completely 
wrong. My question is: what could cause a completely wrong result of 
photon calculation for PPs which look fine in ld1 code test? 

I don't think I messed up the converting. But if anyone would like to 
help, just let me know and I will send you the converted PPs for your 
testing.

Another thing is that although pbe-rrkjus PPs produced best results, 
they also produced negative frequencies, is it normal? In all cases I 
ran a "relax" calculation first to make sure the geometry was optimized. 

I am learning everything in solid states calculations, so any comments 
are welcome and will be greatly appreciated!

James Mao
------------
Postdoc, Department of Chemistry
University of Pittsburgh
------------

Here is the all electron results:
   [cm-1]  
     641
    1373
    2438

results from pbe-rrkjus PPs:

# mode   [cm-1]    [THz]      IR
    1   -188.02   -5.6368    0.0000
    2   -188.02   -5.6368    0.0000
    3      0.00    0.0000    0.0000
    4      0.00    0.0000    0.0000
    5      0.00    0.0000    0.0000
    6    658.64   19.7456    0.4938
    7    658.64   19.7456    0.4938
    8   1304.71   39.1142    0.0000
    9   2340.86   70.1772   12.1795

results from NC LDA PPs I generated using PSLibrary code:

# mode   [cm-1]    [THz]      IR   
    1      0.00    0.0000    0.0000
    2      0.00    0.0000    0.0000
    3      0.00    0.0000    0.0000
    4    218.30    6.5444    0.0000
    5    218.30    6.5444    0.0000
    6    577.10   17.3010    0.0521
    7    577.10   17.3010    0.0521
    8   1303.15   39.0676    0.0000
    9   2386.77   71.5536   11.0101

results (WRONG!) from LDA PPs converted from Abinit fhi files:

# mode   [cm-1]    [THz]      IR
    1   -219.57   -6.5825    0.0000
    2   -219.57   -6.5825    0.0000
    3      0.00    0.0000    0.0000
    4      0.00    0.0000    0.0000
    5      0.00    0.0000    0.0000
    6    246.28    7.3833    0.1700
    7    246.28    7.3833    0.1700
    8    499.18   14.9652    0.0000
    9    675.29   20.2448    9.8485

rlx input:

 &control
    calculation='relax',
    restart_mode='from_scratch',
    prefix='co2'
    pseudo_dir='./pseudos'
    outdir='./'
    tprnfor = .true.
 /
 &system
    ibrav = 1, celldm(1) =20.0, nat=  3, ntyp= 2,
    ecutwfc = 30.0, ecutrho = 300.0
 /
 &electrons
    mixing_beta = 0.7
    conv_thr =  1.0d-8
 /
 &ions
    ion_dynamics="bfgs",
 /
ATOMIC_SPECIES
 C  12.01 06-C.LDA.fhi.UPF
 O  16.01 08-O.LDA.fhi.UPF
ATOMIC_POSITIONS (angstrom)
 C     0.000000     0.000000     0.000000
 O     0.000000     0.000000     1.220000
 O     0.000000     0.000000    -1.220000
K_POINTS (automatic)
1 1 1 0 0 0