<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Center for Informatics

We review recent findings of metal (M) encapsulated caged clusters of Si and Ge obtained from computer experiments based on an ab initio pseudopotential method. It is shown that one M atom changes drastically the properties of Si and Ge clusters and that depending upon the size of the M atom, cages of 14, 15 and 16 Si as well as Ge atoms are formed. In particular M@Si16 silicon fullerene has been obtained for M = Zr and Hf, while a Frank-Kasper polyhedron has been obtained for M$\Xi$16, X = Si and Ge. These clusters show high stability and large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gaps which are likely to make these species strongly abundant. A regular icosahedral M$\Xi$12 cluster has also been obtained for X = Ge and Sn by doping a divalent M atom. Interactions between clusters are rather weak. This is attractive for developing self-assembled cluster materials.

Fulltext

Bulletin of Materials Science

Novel caged clusters of silicon: Fullerenes, Frank-Kasper polyhedron and cubic

This article focuses on the development of a multiobjective optimization algorithm for a tubular reactor-regenerator system with a moving deactivating catalyst. The task is to find the optimal temperature profile along the tubular reactor, catalyst recycle ratio, and the regeneration capacity for maximizing the process profit flux, selectivity, and conversion. A new heuristic technique, viz, ant colony optimization method has been employed to obtain the Pareto optimal set of solutions.

World University root node

Petroleum Science and Technology

Multiobjective optimization of reactor-regenerator system using ant algorithm

[Formula Presented] and [Formula Presented] are very stable molecules with high ionization potentials and low electron affinities. Yet, we report the findings of higher aluminum hydrides, [Formula Presented] [Formula Presented] with cyclic or linear polymeric structures that are even more stable. These represent the possibilities of associating higher contents of hydrogen with aluminum clusters. We use first-principles calculations with a plane-wave basis as well as a linear combination of atomic-orbitals method. The binding energies and the highest occupied–lowest unoccupied molecular-orbital gaps of these molecules are significantly higher as compared to the values for the three-dimensional structures of hydrogenated aluminum clusters. The energetic and fragmentation behavior shows that these molecules should be stable up to a size of at least [Formula Presented] in cyclic or polymeric forms. {\textcopyright} 2003 The American Physical Society.

Physical Review A - Atomic, Molecular and Optical Physics

Cyclic and linear polymeric structures of [Formula Presented] (n=3–7) molecules

We have carried out ab initio calculations on clusters of Pd with 2-23, 55 and 147 atoms using ultrasoft pseudopotential plane wave method and spin-polarized generalized gradient approximation for the exchange-correlation energy. It is found that these clusters have an icosahedral growth and size dependent oscillatory magnetic moments. Atomically closed shell 13, 55 and 147 atom clusters have large moments of 8, 26 and 60 $\mu$B, respectively. But cubic Pd55 has a small moment of 10 $\mu$ B only. This shows the importance of the icosahedral structure in the development of magnetism in Pd clusters. The magnetic energy is, however, small and the moments get quenched by H adsorption. Similar studies have been carried out on Rh and Ru clusters. In the atom these have large moments as compared to zero for Pd and therefore, the moments on clusters are also large. However, the moments decrease rapidly as the size grows.

European Physical Journal D

Magnetism in clusters of non-magnetic elements: Pd, Rh and Ru - Magnetism in clusters of non-magnetic elements

Absolute values of the quasiparticle energies of small silicon clusters (Sin, n=4,5,6) are determined quite accurately by means of the state-of-the-art ab initio calculations in the GW approximation, under the all-electron mixed-basis representation. We find that the electron affinity, which is very sensitive to the ionic valence and the cluster geometry, depends strongly on the photoemission process and that the time-reversal symmetry is completely broken between the photemission and its inverse process. This is due to large structural changes in Si5- and Si6- as compared to the neutral clusters. When appropriate structural energy changes are taken into account, the time-reversal symmetry is satisfied and all results agree excellently with the preexisting experimental data. {\textcopyright} 2003 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Breakdown of time-reversal symmetry of photoemission and its inverse in small silicon clusters

Physical Review-Section B-Condensed Matter

{Surface physics, low-dimensional systems and related topics-Ab initio calculations of electronic structures, polarizabilities, Raman and infrared spectra, optical gaps and {\ldots}}

Applied Physics Letters

Metal-doped magic clusters of Si, Ge and Sn: The finding of a magnetic superatom

The availability of high performance computers and development of efficient algorithms has led to the emergence of computational materials science as the third branch of materials research complementing the traditional theoretical and experimental approaches. It has created new virtual realities in materials design that are either experimentally not realizable easily or are prohibitively expensive. The possibilities of doing calculations from first principles have led to predictive capabilities that open up new avenues of discovering novel materials with desired properties, understanding material behaviour on the nano- to the macroscopic scale and helping research in new frontiers that could interface between nano-materials and drug design, as well as in understanding biological systems. Here, we describe some significant recent developments related to alloy and steel design as well as the study of matter on the nano-scale - an area that has gained much prominence in current materials research.

Sadhana - Academy Proceedings in Engineering Sciences

Computational materials science: The emergence of predictive capabilities of material behaviour

Ab initio calculations of H interaction on [Formula presented], [Formula presented] ([Formula presented], Mo and W) and [Formula presented] fullerene ([Formula presented]) show relatively weak binding of H in agreement with experimental results of H free [Formula presented] and [Formula presented] clusters. Adsorption of H enhances [Formula presented] bonding between the Si atoms, weakens the [Formula presented] cage interactions and leads to distortions in the cages. [Formula presented] has [Formula presented] magnetic moment in contrast to zero for [Formula presented]. Removal of the [Formula presented] atom leads to stable empty cages of [Formula presented], [Formula presented] and [Formula presented] with large highest occupied–lowest unoccupied molecular orbital gaps of 2.5–3.0 eV, making them attractive for optoelectronic applications. {\textcopyright} 2003 The American Physical Society.