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Shiv Nadar University

(SoNS) School of Natural Sciences

One- and two-dimensional cellular automata (CA) simulations of neutral "atoms," viewed as "complex" distributions of electron density around a central nucleus, are performed in order to explore CA-based discretized and connectionist approaches to the synthesis and structure-dynamics problems of many-electron systems. A link between CA and the quantum mechanics of atoms is made by taking the Thomas-Fermi theory as an illustrative example. Starting from a nonstationary distribution, the stationary distribution of electron density around a nucleus arises out of a natural stability criterion described through CA rules. © 1996 John Wiley & Sons, Inc.

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Chemistry

International Journal of Quantum Chemistry

"Atom" as a complex system: One- and two-dimensional cellular automata simulations

Hydrogen is the lightest element in nature, and so, its detection and quantitative analysis is difficult by the conventional methods utilized for other elements. In the recent years the technique of elastic recoil detection analysis (ERD) using 1-2 MeV He+ beam has been developed to quantitatively and simultaneously analyze hydrogen and its isotopes in solids. Such a facility has been set up using the 2 MeV Van-de-Graaff accelerator at IIT Kanpur. It facilitates H and D analysis in a material up to a depth of ∼1 μm with a detection sensitivity of 0.1 at.% and depth resolution of about 300 Å. The application potential of this setup is illustrated by presenting the results of measurements performed on Al:H:D systems prepared by plasma source ion implantation and high TC YBCO pellets exposed to humid atmosphere.

Physics

Fulltext

Bulletin of Materials Science

ERD facility for analysis of hydrogen and deuterium in solids

This letter reports room-temperature synthesis by ion beam mixing of the ε1-Cu3Ge phase which is a promising candidate for interconnect and contact material in very large scale integrated circuit technology. The resistivity of the mixed sample was found to be nearly the same as the one obtained from thermally prepared films. We briefly discuss the likely mechanisms of phase formation and conclude that reaction kinetics dominates over thermodynamic forces during phase formation. The sequence of phase formation is explained by effective heat of formation rule.© 1995 American Institute of Physics.

Applied Physics Letters

Room-temperature synthesis of copper germanide phase by ion beam mixing

The dynamics of Jahn–Teller systems has recently been discussed in terms of generalized electronic charge and current densities in nuclear‐coordinate space. The introduction of the electronic phase as a function of both electronic and nuclear coordinates, in addition to the electronic density, was a crucial component of this formulation. Here, a densitybased treatment of Born couplings is derived from first‐principles quantum mechanics beyond the Born–Oppenheimer approximation. Because of the degenerate electronic configuration of a Jahn–Teller molecule, there are an infinite number of ways in which the charge distribution can be oriented for the same energy, leading to a vanishing bond hardness for the molecule in the symmetric nuclear configuration. Further, the moving nuclear framework serves as the perturbation necessary to define the orientation of the charge density, leading to unhindered rotation of the charge cloud. This leads to the dynamical Jahn–Teller problem, namely, the coupling of electronic and nuclear motions through the Born coupling terms. Applications to superconductivity theory are discussed. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc.

Density functional theory of born couplings: Consequences for electron flow in Jahn–Teller molecules and superconductors

Progress of Theoretical Physics

SO(2, 1), Supersymmetry and D-Dimensional Radial Schrodinger Equation

We report the results of ab initio calculations of the nonadiabatic Born coupling terms for the two lowest-lying singlet A″ excited states of ozone (1A2 and 1B1 in C2v symmetry) whose electronic potential energy surfaces exhibit a crossing at a bond angle near 120°. Since photoexcitation from the ground state to these A″ states is believed to be responsible for the Chappuis band of ozone, determination of the nonadiabatic coupling terms in the molecular Hamiltonian is therefore likely to be of importance in understanding the predissociative features of the spectrum. The nuclear derivative coupling matrix elements are computed between ab initio electronic wavefunctions obtained from multi-reference configuration interaction (MRD-CI) calculations in a basis of configuration state functions constructed from MCSCF orbitals. The first-derivative nonadiabatic coupling terms are calculated analytically in a manner similar to the calculation of analytic energy gradients, thereby avoiding the cumbersome numerical differentiation of CI and SCF coefficients. The calculated analytical derivative coupling matrix elements are used to determine a suitable transformation to a quasidiabatic basis. © 1995 Elsevier Science B.V. All rights reserved.

Chemical Physics

Nonadiabatic coupling of the 1 1A″ and 2 1A″ states of ozone

In this Letter some basic properties of a truncated oscillator are studied. By using finite-dimensional representation matrices of the truncated oscillator we construct new parasupersymmetric schemes and remark on their relevance to the transition operators of the non-interacting N-level system endowed with bosonic modes. © 1995.

Physics Letters A

A new look at the harmonic oscillator problem in a finite-dimensional Hilbert space

Some implications of a generalized quantum condition in connection with supersymmetric quantum mechanics are studied. By defining suitable representations for the supercharges in terms of the Pauli matrices I show that Brzeziński et al.'s recent scheme of a modified oscillator can be extended to a wider class of superpotentials. © 1994.