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A study of the structure and the bonding nature of Mg clusters having 2 to 13 atoms has been made using the density functional molecular dynamics method within the local density approximation. The calculated lowest energy structures can be described in terms of a tetrahedron and a trigonal prism. Mg4 and Mg10 are magic clusters and Mg13 is neither an icosahedron nor a cuboctahedron. The bonding nature varies from atom to atom in a cluster and the transition from weakly bonded dimer to bulk like metallic behaviour is oscillatory and slow. {\textcopyright} 1991 Springer-Verlag.

World University root node

Zeitschrift f{\"{u}}r Physik D Atoms, Molecules and Clusters

A density functional molecular dynamics study of the bonding and stability of Mgn clusters (n=2-13)

The structure, growth and bonding nature of Mgn (n=213) clusters is studied using the density-functional molecular-dynamics method and the simulated annealing technique within the local-density approximation. We find a tetrahedron and a trigonal prism as two important constituents of the structure of Mg clusters to which atoms can be added by capping the faces. Mg13 is neither an icosahedron nor a cuboctahedron. The lowest-energy structure of Mg13 that we obtained from our simulated annealing can be considered as fusion of Mg9 and Mg4 clusters. This is nearly degenerate with the relaxed hcp structure and suggests the possibility of a path for transition to hcp structure for bigger clusters. We find Mg4 and Mg10 to be the magic clusters, which is in general agreement with the predictions of the jellium model of metal clusters. However, calculations of the charge densities, the p character and the gap between the highest occupied and the lowest unoccupied states suggest the presence of mixed bonding character in Mg clusters and an oscillatory and slow convergence to bulk metallic behavior. {\textcopyright} 1991 The American Physical Society.

Physical Review B

Structure, growth and bonding nature of Mg clusters

Using multifractal analysis we study extended, self-similar and non-self-similar type of wave functions in the Fibonacci model. Extended states arising due to commutation of transfer matrices for certain blocks of atoms in quasiperiodic systems are shown to have the same signature as the Bloch states in terms of the singularity spectrum with f($\alpha$)=$\alpha$=1. Numerically, however, the extended states show a typical multifractal behaviour for finite chain lengths. Finite size scaling corrections yield results consistent with that obtained analytically. The self-similar states at the band edges show a multifractal behaviour and they are energy dependent in the case of blocks of atoms arranged in a Fibonacci sequence. For non-self-similar states we obtain a non-monotonic behaviour of f($\alpha$) as a function of the chain length. We also show that in cases where extended states exist, the cross-over from extended to non-self-similar states in gradual. {\textcopyright} 1991 the Indian Academy of Sciences.

Pramana

A multifractal study of wave functions in 1-D quasicrystals

The electronic structure of two-component Penrose models of quasicrystals is studied by using a tight-binding model. The Penrose lattice is subdivided in non-equivalent sublattices and the local density of states are calculated at a site surrounded by clusters of distinct sizes. The strong dependence of the density of states on the cluster size and the local neighborhood is evidenced. In particular, the electronic structure of a decoration proposed to model the T-phase of AlFe, is calculated. An asymmetric density of states with no self-similar behaviour is obtained. {\textcopyright} 1990.

Solid State Communications

Local electronic density of states in two-component penrose lattices

Indira Gandhi Centre for Atomic Research

Materials Science Division progress report 1986-1988

Multiple steady states are known to exist in nonisothermal nonadiabatic systems for a certain range of parameter values. It has been elucidated that in a certain region of Damkohler numbers five steady states classified as kinetic, diffusion and intermediate regimes are possible. The results of the effects of the external fluctuations on the system behaviour are reported in this article. A nonisothermal nonadiabatic tubular reactor was analyzed in the presence of external disturbances. The study, while not revealing any noise induced transitions, clearly shows the preference of evolving states in the presence of noise.

Hungarian Journal of Industrial Chemistry

Analysis of nonisothermal nonadiabatic tubular reactors in the presence of external disturbances

A Comment on the Letter by V. Kumar and G. Ananthakrishna, Phys. Rev. Lett. 59, 1476 (1987). {\textcopyright} 1988 The American Physical Society.

Physical Review Letters

Extended electronic states in a Fibonacci superlattice

A brief review of various types of defects on surfaces and their role in surface reactions is presented. Particular emphasis is given on defects like steps/kinks and additives (promoters and poison). {\textcopyright} 1988 Indian Academy of Sciences.

Bulletin of Materials Science

Defects on surfaces

Ananthakrishna and Kumar reply

An analysis is presented for a gas-solid heterogeneous, noncatalytic reaction which propagates from the center. The results are compared with those for a shrinking-core model. The analysis reveals that the reaction rate.can exhibit a maximum or a discontinuity. For a first-order reaction, the moving reaction interface is always stable toward a one-dimensional perturbation. © 1987, American Chemical Society. All rights reserved.