[Pw_forum] surface relaxation and non-zero parallel forces.
Gisela Bocan
gbocan at gmail.com
Sat Jun 11 04:35:08 CEST 2011
Hello,
I assumed surface relaxation for the Ag(110) surface would be an
easy matter. As it happens, I find non-zero forces parallel to the surface
and therefore, upon relaxation, I get a non-neglectable parallel
displacement of the ions. I am working with a 2x2sqrt(2) unit cell. I attach
my file.in and the forces I get. Note that the forces along one direction
(x) are much larger that along the other one (y). Note as well the large
values considered for ecutwfc, ecutrho, kpoints and the small degauss and
conv_thr. Any ideas on how to correct this behaviour? Am I missing
something? Thanks in advance and sorry if this is a stupid question. Small
changes in the input parameters can lower the forces I get but I find
nothing systematic.
&control
prefix = 't_G0',
outdir = ' ',
pseudo_dir = '/home/qe/pseudo',
calculation = 'scf',
tprnfor = .true.,
lkpoint_dir = .false.,
verbosity = 'high',
/
&system
ibrav = 8,
celldm(1) = 11.1298607358762567,
celldm(2) = 1.4142135623730949,
celldm(3) = 2.25,
nat = 16,
ntyp = 1,
ecutwfc = 45,
ecutrho = 450.00,
occupations = 'smearing',
smearing = 'mv',
degauss = 0.002,
/
&electrons
conv_thr = 1.d-12
diagonalization = 'cg'
/
&ions
/
ATOMIC_SPECIES
Ag 107.8682 Ag.pbe-d-rrkjus.UPF
ATOMIC_POSITIONS crystal
Ag 0.0000000000000000 0.0000000000000000 0.3333333333333333
Ag 0.5000000000000000 0.0000000000000000 0.3333333333333333
Ag 0.0000000000000000 0.5000000000000000 0.3333333333333333
Ag 0.5000000000000000 0.5000000000000000 0.3333333333333333
Ag 0.2500000000000000 0.2500000000000000 0.2222222222222222
Ag 0.7500000000000000 0.2500000000000000 0.2222222222222222
Ag 0.2500000000000000 0.7500000000000000 0.2222222222222222
Ag 0.7500000000000000 0.7500000000000000 0.2222222222222222
Ag 0.0000000000000000 0.0000000000000000 0.1111111111111111
Ag 0.5000000000000000 0.0000000000000000 0.1111111111111111
Ag 0.0000000000000000 0.5000000000000000 0.1111111111111111
Ag 0.5000000000000000 0.5000000000000000 0.1111111111111111
Ag 0.2500000000000000 0.2500000000000000 0.0000000000000000
Ag 0.7500000000000000 0.2500000000000000 0.0000000000000000
Ag 0.2500000000000000 0.7500000000000000 0.0000000000000000
Ag 0.7500000000000000 0.7500000000000000 0.0000000000000000
K_POINTS automatic
33 23 1 0 0 0
atom 1 type 1 force = 0.00000000 0.00000000 -0.01175276
atom 2 type 1 force = 0.00000000 0.00000000 -0.01175282
atom 3 type 1 force = 0.00000000 0.00000000 -0.01175318
atom 4 type 1 force = 0.00000000 0.00000000 -0.01175325
atom 5 type 1 force = -0.00004221 0.00000033 0.01048323
atom 6 type 1 force = 0.00004221 0.00000033 0.01048323
atom 7 type 1 force = -0.00004221 -0.00000033 0.01048323
atom 8 type 1 force = 0.00004221 -0.00000033 0.01048323
atom 9 type 1 force = 0.00000000 0.00000000 -0.01048309
atom 10 type 1 force = 0.00000000 0.00000000 -0.01048306
atom 11 type 1 force = 0.00000000 0.00000000 -0.01048272
atom 12 type 1 force = 0.00000000 0.00000000 -0.01048269
atom 13 type 1 force = -0.00004148 0.00000003 0.01175266
atom 14 type 1 force = 0.00004148 0.00000003 0.01175266
atom 15 type 1 force = -0.00004148 -0.00000003 0.01175266
atom 16 type 1 force = 0.00004148 -0.00000003 0.01175266
Dr. G. A. Bocan
Surface Physics Group,
Centro Atómico Bariloche,
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