QE.Alad.Al100.d

Diffusion of an aluminum adatom on the hollow site of the aluminum (100) surface (the system consists of 151 atoms). Two searches are used, the first one corresponds to the exchange mechanism, and the second to the hopping mechanism.

Description: The starting configuration is an Al adatom adsorbed in the hollow site on the Al(100) surface. The run_example.sh generates the two inputs for ARTn searches, for the exchange mechanism two atoms are displaced; the adatom (index 1) and one of its nearest neighbors (index 14), The direction of the initial push is constrained so that the adatom approaches the position of the displaced nearest neighbor, and the nearest neighbor is displaced twoards a hollow site and the eigenvalu threshold is lowered, because the eigenvalue of the eignevector associated to the saddle point is greater than the default threshold (-0.01):

push_mode = 'list'
push_ids = 1, 14
add_const(:,1) = 1.0, 1.0, -1.0, 0.0
add_const(:,14) = 1,0, 1.0, 1.0, 0.0
eigval_thr = -0.005

For the second search, only the adatom is displaced in the direction twoards one of the nearest hollow sites

push_mode = 'list'
push_ids = 1
add_const(:,1) = 0.0, 1.0, 0.0, 0.0

Launch command:

To launch this example simply run:

./run_example.sh

Warning

This example is computationally very demanding and should only be run on a dedicated machine, utilizing the parallelization capabilities of QE by setting the appropriate number of cores in run_example.sh. The default value is set to 8 cores, note that a single search running on 16 cores (Intel-Xeon W2295 CPU 3.00GHz) consumes about 5 hours of wall time.

Expected results: If the example concludes succesfully you should obtain two saddle points, one for the exchange mechanism of Al adatom diffusion, with a barrier of 0.38 eV and one for the hopping mechanism, with a barrier of 0.54 eV. An example of a succesfull run (along with the files generated) is available in the reference.d folder.