Model System
The test problem is a 7 atoms island on the (111) surface of an FCC metal.
All saddle points lead from this close packed heptamer (shown in red) to some
adjacent state. All the atoms in this simulation are identical. The interaction
between the atoms is a very simple pairwise additive Morse potential.
V(r) = A [ e-2 a ( R - R0 ) - 2 e- a ( R - R0
) ]
This potential is shifted by V(RC) where RC = 9.5 Å is
the cutoff distance. The parameters for the Morse potential were chosen to reproduce
diffusion barriers on Pt surfaces.
A = 0.7102 eV
a = 1.6047 Å-1
R0 = 2.8970 Å
The surface is simulated with a 6 layer slab, each layer containing 56 atoms.
The mimimum energy lattice constant for the FCC solid is used, 2.74412 Å. The
bottom three layers in the slab are frozen. A total of 7 + 165 = 175 atoms are
free to move.
The configurations of the low energy saddles leading from the compact island
(in our local con format) are available here.
In this file, each process has three configurations. The 5th lowest energy process,
for example, would be a process connecting min05a.con and min05b.con through
the saddle sp05.con. For each con file, there is also an eps file which shows
a top view of the island. The path.dat files have a list of energy values along
the minimum energy path for each process.
Compiled Results
| CI NEB | sd | qm | fire | cg | lbfgs(lineopt) | lbfgs(hess) | glbfgs(lineopt) | glbfgs(hess) | rk4 |
|---|---|---|---|---|---|---|---|---|---|
| FC (0.01) | 412 | 190 | 77 | 111 | 108 | 351 | 100 | 49 | ?? |
| FC (0.001) | 737 | 354 | 116 | 169 | 154 | 428 | 147 | 73 | ?? |
| CI-DNEB | sd | qm | fire | cg | lbfgs(lineopt) | lbfgs(hess) | glbfgs(lineopt) | glbfgs(hess) | rk4 |
| FC (0.01) | 411 | 194 | 78 | 108 | 115 | ?? | 104 | 47 | ?? |
| FC (0.001) | 727 | 351 | 117 | 145 | 151 | ?? | 160 | 74 | ?? |
| CI Old String | sd | qm | fire | cg | lbfgs(lineopt) | lbfgs(hess) | glbfgs(lineopt) | glbfgs(hess) | rk4 |
| FC (0.01) | 410 | 190 | 92 | 143 | 144 | 81 | 93 | 42 | 786 |
| FC (0.001) | 725 | 334 | 146 | 208 | 219 | 195 | 144 | 63 | 1230 |
| Old String | sd | qm | fire | cg | lbfgs(lineopt) | lbfgs(hess) | glbfgs(lineopt) | glbfgs(hess) | rk4 |
| FC (0.01) | 421 | 194 | 82 | 126 | 168 | 140 | 100 | 41 | 900 |
| FC (0.001) | 775 | 358 | 148 | 202 | 264 | 338 | 159 | 61 | 1376 |