[Pw_forum] Cannot reproduce standard CO/Au(111) adsorption energy

[Janesko, Benjamin]

> On Jun 25, 2010, at 19:34 , Janesko, Benjamin wrote:
> 
> > Everything looks reasonable in XCrysDen
> 
> and what is the C-Au or O-Au distance? it seems to me that the CO
> molecule is very far away from the gold surface. If so, it is normal to
> find very small binding energies
> 
> P.
> ---
> Paolo Giannozzi, Dept of Physics, University of Udine

I've rerun from a different starting geometry, and it only partially solved the problem. The optimum C-Au distance is now 2.24 Angstrom, and the new CO-Au(111) adsorption energy is -0.003978 Rydberg = -0.055 eV. Again, this is much smaller than the PBE CO/Au adsorption energy -0.26 eV from Quantum Espresso calculations reported in PRB 77, 085414 (2008). I've done some potential energy surface scans with rigid CO and Au groups, and haven't seen anything helpful. I've attached my CO/Au(111) input file below. Any further explanations of how my calculations differ from the above reference would be appreciated. Thanks again. 

  - BGJ 

&control
    calculation='relax'
    prefix='coau5-3x3-fcc3',
    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   4.317809266452 1 1 1
O        0.333333333   0.000000000   4.546726732327 1 1 1
K_POINTS automatic
8 8 1 0 0 0



===================
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)
******************