Dear QE experts,
I am just starting to use pwscf for surface chemistry research. I've begun by
attempting to reproduce the CO/Au(111) adsorption energy in de Gironcoli et al,
PRB 77, 085414 (2008). My problem is that my PBE adsorption energy is an order
of magnitude lower than any I've seen in the literature! And I can't figure out
what I'm doing wrong.
I've prepared a 5-layer slab of Au(111) at the experimental bulk lattice
parameter (2.884 Angstrom Au-Au spacing):
---------------------------------------
&control
calculation='relax'
prefix='au5-3x3',
pseudo_dir = '/home/bjanesko2/espresso/pseudo//',
outdir='/tmp/espresso/'
/
&system
ibrav=4,
celldm(1)=9.439624066,
celldm(3)=8.0,
nat=15,
ntyp=1,
ecutwfc = 40.0,
ecutrho = 250.0,
occupations='smearing', smearing='marzari-vanderbilt', degauss=0.01
/
&electrons
conv_thr=0.0000001
/
&ions
ion_dynamics='bfgs',
path_thr=0.03
/
ATOMIC_SPECIES
Au 196.966 Au.pbe-nd-van.UPF
ATOMIC_POSITIONS alat
Au 0.000000 0.000000 4.000000 1 1 1
Au 0.500000 0.288675 4.000000 1 1 1
Au 1.000000 0.577350 4.000000 1 1 1
Au 0.333333 0.000000 3.528595 1 1 1
Au 0.833333 0.288675 3.528595 1 1 1
Au 1.333333 0.577350 3.528595 1 1 1
Au 0.666667 0.000000 3.057191 0 0 0
Au 1.166667 0.288675 3.057191 0 0 0
Au 1.666667 0.577350 3.057191 0 0 0
Au 1.000000 0.000000 2.585786 0 0 0
Au 1.500000 0.288675 2.585786 0 0 0
Au 2.000000 0.577350 2.585786 0 0 0
Au 1.333333 0.000000 2.114382 0 0 0
Au 1.833333 0.288675 2.114382 0 0 0
Au 2.333333 0.577350 2.114382 0 0 0
K_POINTS automatic
8 8 1 0 0 0
----------------------------------------------------
and CO adsorbed to the fcc site, in a sqrt(3) x sqrt(3) overlayer (1/3 ML
coverage)
-------------------------------------------------------
&control
calculation='relax'
prefix='coau5-3x3-hcp',
pseudo_dir = '/home/bjanesko2/espresso/pseudo//',
outdir='/tmp/espresso/'
/
&system
ibrav=4,
celldm(1)=9.439624066,
celldm(3)=8.0,
nat=17,
ntyp=3,
ecutwfc = 40.0,
ecutrho = 250.0,
occupations='smearing', smearing='marzari-vanderbilt', degauss=0.01
/
&electrons
conv_thr=0.0000001
/
&ions
ion_dynamics='bfgs',
path_thr=0.03
/
ATOMIC_SPECIES
Au 196.966 Au.pbe-nd-van.UPF
C 12.0107 C-pbe-van_ak.UPF
O 15.9994 O-pbe-van_ak.UPF
ATOMIC_POSITIONS alat
Au 0.000000 0.000000 4.000000 1 1 1
Au 0.500000 0.288675 4.000000 1 1 1
Au 1.000000 0.577350 4.000000 1 1 1
Au 0.333333 0.000000 3.528595 1 1 1
Au 0.833333 0.288675 3.528595 1 1 1
Au 1.333333 0.577350 3.528595 1 1 1
Au 0.666667 0.000000 3.057191 0 0 0
Au 1.166667 0.288675 3.057191 0 0 0
Au 1.666667 0.577350 3.057191 0 0 0
Au 1.000000 0.000000 2.585786 0 0 0
Au 1.500000 0.288675 2.585786 0 0 0
Au 2.000000 0.577350 2.585786 0 0 0
Au 1.333333 0.000000 2.114382 0 0 0
Au 1.833333 0.288675 2.114382 0 0 0
Au 2.333333 0.577350 2.114382 0 0 0
C 0.333333333 0.000000000 5.309331423 1 1 1
O 0.333333333 0.000000000 5.544873192 1 1 1
K_POINTS automatic
8 8 1 0 0 0
---------------------------------------------------
The pseudopotentials are all from the Quantum Espresso website, and are used
without modification. I get total energies at optimized geometries of
-43.3739979804 Ry for an isolated CO molecule, -1530.4827281024 Ry for the Au
slab, and -1573.8569359340 Ry for CO on the slab. Everything looks reasonable
in XCrysDen. Am I doing something obviously wrong?
Thanks,
Ben J.
===================
Benjamin G. Janesko
Assistant Professor
Department of Chemistry
Texas Christian University
Office: SWR 428
http://personal.tcu.edu/bjanesko/
b.janesko at tcu.edu
Phone: 1-817-257-6202
Fax: 1-817-257-5851 (attn:janesko)
