Chemistry Reference
In-Depth Information
APPENDIX CALCULATION DETAILS
All calculations in this chapter used the PBE GGA functional. For calculations
related to Cu surfaces, a cutoff energy of 380 eV and the Methfessel -Paxton
scheme was used with a smearing width of 0.1 eV. For calculations related to
Si surfaces, the cutoff energy was 380 eV and Gaussian smearing with a width
of 0.1 eV was used. The
k
points were placed in reciprocal space using the
Monkhorst-Pack scheme. For all surface calculations, the supercell dimen-
sions in the plane of the surface were defined using the DFT-optimized bulk
lattice parameter.
Section 4.5
Surface relaxations were examined using asymmetric slab
models of five, six, seven, or eight layers with the atoms in the two
bottom layers fixed at bulk positions and all remaining atoms allowed
to relax. For Cu(100), the supercell had c(2
2) surface symmetry, con-
taining 2 atoms per layer. For Cu(111), (
p
p
)R30
surface unit cell
with 3 atoms per layer was used. All slab models included a minimum of
23
˚
of vacuum along the direction of the surface normal. A 6
6
1
k
-point mesh was used for all calculations.
Section 4.6
The calculations of the surface energy were as in Section 4.5,
with the addition of the energy calculation of Cu in the bulk phase. The
bulk calculation was carried out on an fcc primitive cell with the DFT-
optimized lattice parameter using 11
11
11
k
points.
Section 4.8
The reconstructed Si(001) surface was modeled using a c(4
4) asymmetric slab with four layers. The bottom two layers were fixed at
bulk positions. Reciprocal space was sampled with 11
11
11
k
points
and the vacuum spacing was 17
˚
.
Section 4.9
The Cu(100) c(4
4)-H overlayer was examined using a
four-layer asymmetric slab with the bottom two layers fixed at bulk pos-
itions and 6
6
1
k
points.
Section 4.10
The calculations of H adsorption on Cu(100) as a function of
coverage were carried out on four-layer slabs of c(1
1), c(2
2), and
c(4
4) symmetry using
k
point meshes of 16
16
1, 12
12
1, and
6
6
1, respectively. The calculation of H
2
was carried out in a box
of edge length 20
˚
. The optimized H
2
bond length was 0.75
˚
.
8
