Equilibrium geometries and associated energetic properties of mixed metal- silicon clusters from global optimization

摘要

The structural properties of the cluster series MemSi7-m (Me=Cu and Li, m ≤ 6) are studied by density functional theory (DFT) employing a plane wave basis. The equilibrium geometries and energetic properties of these clusters are obtained by use of the simulated annealing procedure in conjunction with the Nosé thermostat algorithm. The lowest energy isomer thus obtained is analyzed by Density Functional Theory at the B3LYP/6−311+G(d,p) level including all electrons. Pentagonal ground state structures derived from the D5h equilibrium geometries of both Si7 and Cu7 are obtained for CumSi7-m with m < 6. The LimSi7-m clusters, in contrast, tend towards adsorption geometries where m Li atoms are attached to a Si7-m framework with pronounced negative charge. For both LimSi7-m and CumSi7-m, a marked decrease of the energy gap is found as the number of metal atom constituents increases. 61.46.+w, 73.22.-f, 36.40.Qv, 36.40.Cg