Investigation of strain relaxation mechanism in small SiGe clusters

We have performed a systematic search for the ground-state geometry of Sin Gem neutral clusters (n + m = 3–5, 7). A number of low-energy geometric isomers were optimized using reliable total-energy calculations through B3LYP hybrid method. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. Due to its larger size, the replacement of a silicon atom by a germanium one generates strain that affects the atomic configurations. Our results indicate that a bond-stretching mechanism is the dominant effect that determines the geometry of the clusters. Our calculations have shown that as the number of Ge atoms increases, the average interatomic distance among all atoms in the cluster grows linearly. Such behavior can be understood as a cluster analog to Vegard's law for alloys. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)