Articles written in Bulletin of Materials Science
Volume 26 Issue 1 January 2003 pp 117-121
We present results for ground state structures and properties of small hydrogenated silicon clusters using the Car–Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si–H–Si bond connecting two silicon atoms. We find that in the case of a compact and closed silicon cluster hydrogen bonds to the silicon cluster from outside. To understand the structural evolutions and properties of silicon cluster due to hydrogenation, we have studied the cohesive energy and first excited electronic level gap of clusters as a function of hydrogenation. We find that first excited electronic level gap of Si𝑛 and Si𝑛H fluctuates as function of size and this may provide a first principle basis for the short-range potential fluctuations in hydrogenated amorphous silicon. The stability of hydrogenated silicon clusters is also discussed.
Volume 26 Issue 1 January 2003 pp 123-125
The ground state structures and properties of Si3H𝑛 (1 ≤ 𝑛 ≤ 6) clusters have been calculated using Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as a function of hydrogenation. Hydrogenation is done till all dangling bonds of silicon are saturated. Our results show that over coordination of hydrogen is favoured in Si3H𝑛 clusters and the geometry of Si3 cluster does not change due to hydrogenation. Cohesive energy per particle and first excited electronic level gap study of the clusters show that Si3H6 cluster is most stable and Si3H3 cluster is most unstable among the clusters considered here.
Volume 26 Issue 1 January 2003 pp 127-130
We discuss the application of biologically inspired genetic algorithms to determine the ground state structures of a number of Si–H clusters. The total energy of a given configuration of a cluster has been obtained by using a non-orthogonal tight-binding model and the energy minimization has been carried out by using genetic algorithms and their recent variant differential evolution. Our results for ground state structures and cohesive energies for Si–H clusters are in good agreement with the earlier work conducted using the simulated annealing technique. We find that the results obtained by genetic algorithms turn out to be comparable and often better than the results obtained by the simulated annealing technique.
Volume 26 Issue 1 January 2003 pp 143-146
We present an
Volume 26 Issue 1 January 2003 pp 147-150
We present first-principles calculations of the relative energies of various phases of lithiated manganese oxides with and without Co. We use the ultrasoft pseudopotential method as implemented in the Vienna
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