[Pw_forum] SCAN + rVV10

[Claudio Antonio Perottoni]

Hi,

I am giving a try to SCAN+rVV10 using the master branch of QE available at
https://github.com/QEF/q-e as of Sept. 24, 2017 (PWSCF v.6.2MaX). QE was
compiled against libxc (trunk version > 3.0.0) and rVV10 kernel table was
generated by *generate_rVV10_kernel_table.x* and copied to the pseudo dir.
As a test case, I chose hexagonal boron nitride.

The issue I am facing with is that pw.x returns the same energies for
input_dft = 'scan' and for input_dft = "scan+sla+pw+rw86+pbc+vv10" (i.e.,
for SCAN + rVV10). The code seems to identify correctly the string given to
input_dft (e.g., for input_dft = 'scan' the output file gives
"Exchange-correlation = SCAN ( 0 0 0 0 0 5)" and, for input_dft =
"scan+sla+pw+rw86+pbc+vv10", the output files gives "Exchange-correlation =
SCAN+SLA+PW+RW86+PBC+VV10 ( 1 4 13 4 3 5)"). In both cases, however, I got
exactly the same energy after SCF convergence.

Using the same input file with just rVV10 worked like a charm, giving a
good estimate for the hexagonal boron nitride interplanar distance.
Furthermore, when running pw.x with input_dft = 'rVV10' (or, for that
matter, "sla+pw+rw86+pbc+vv10") I got the following in the output file:

Carrying out rVV10 run using the following parameters:
Nqs = 20 Nr_points = 1024 r_max = 100.000
b_value = 6.30000 beta = 0.00901
q_mesh = 0.00010000 0.00030000 0.00058939 0.00100810
0.00161396 0.00249058 0.00375900 0.00559430
0.00824984 0.01209221 0.01765183 0.02569619
0.03733578 0.05417739 0.07854596 0.11380545
0.16482331 0.23864234 0.34545298 0.50000000

The above message does not appears in the output file when using input_dft
= "scan+sla+pw+rw86+pbc+vv10".


Here is the input file I am using in these tests:

&CONTROL
title = 'hBN'
calculation = 'scf'
restart_mode = 'from_scratch'
outdir = './files'
wfcdir = './files'
pseudo_dir = "../pseudo"
prefix = 'hbn'
disk_io = 'default'
verbosity = 'default'
nstep = 400
/

&SYSTEM
space_group = 194
a = 2.503374
c = 6.80
origin_choice = 1
nat = 2
ntyp = 2
ecutwfc = 120
ecutrho = 480
input_dft = "scan+sla+pw+rw86+pbc+vv10"
/

&ELECTRONS
electron_maxstep = 200
conv_thr = 1.0D-9
diago_thr_init = 1e-4
startingpot = 'atomic'
startingwfc = 'atomic'
mixing_mode = 'plain'
mixing_beta = 0.5
mixing_ndim = 8
diagonalization = 'david'
/

ATOMIC_SPECIES
B 10.8110000000 B.pbe-hgh.UPF
N 14.0067000000 N.pbe-hgh.UPF

ATOMIC_POSITIONS crystal_sg
B 0.33333333333333 0.66666666666667 0.25000000000000
N 0.33333333333333 0.66666666666667 0.75000000000000

K_POINTS automatic
21 21 7 0 0 0

It seems that rVV10 is not being used at all in calculations with input_dft
= "scan+sla+pw+rw86+pbc+vv10". Maybe this is an invalid combination of
keywords?

Regards,
Claudio

-- 
*********************************************************************
Claudio A. Perottoni

Universidade de Caxias do Sul
Rua Francisco Getúlio Vargas, 1130
95070-560 Caxias do Sul - RS - Brazil
*********************************************************************



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