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Rahul Sharma

Bio: Rahul Sharma is an academic researcher from St. Xavier's College-Autonomous, Mumbai. The author has contributed to research in topics: Wave packet & Simulated annealing. The author has an hindex of 12, co-authored 27 publications receiving 322 citations. Previous affiliations of Rahul Sharma include Indian Association for the Cultivation of Science & University of Coimbra.

Papers
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Journal ArticleDOI
TL;DR: The workability of beyond Born-Oppenheimer theory to construct diabatic potential energy surfaces (PESs) of a charge transfer atom-diatom collision process has been explored by performing scattering calculations to extract accurate integral cross sections (ICSs) and rate constants for comparison with most recent experimental quantities.
Abstract: The workability of beyond Born-Oppenheimer theory to construct diabatic potential energy surfaces (PESs) of a charge transfer atom-diatom collision process has been explored by performing scattering calculations to extract accurate integral cross sections (ICSs) and rate constants for comparison with most recent experimental quantities. We calculate non-adiabatic coupling terms among the lowest three singlet states of H3+ system (11A', 21A', and 31A') using MRCI level of calculation and solve the adiabatic-diabatic transformation equation to formulate the diabatic Hamiltonian matrix of the same process [S. Mukherjee et al., J. Chem. Phys. 141, 204306 (2014)] for the entire region of nuclear configuration space. The nonadiabatic effects in the D+ + H2 reaction has been studied by implementing the coupled 3D time-dependent wave packet formalism in hyperspherical coordinates [S. Adhikari and A. J. C. Varandas, Comput. Phys. Commun. 184, 270 (2013)] with zero and non-zero total angular momentum (J) on such newly constructed accurate (ab initio) diabatic PESs of H3+. We have depicted the convergence profiles of reaction probabilities for the reactive non-charge transfer, non-reactive charge transfer, and reactive charge transfer processes for different collisional energies with respect to the helicity (K) and total angular momentum (J) quantum numbers. Finally, total and state-to-state ICSs are calculated as a function of collision energy for the initial rovibrational state (v = 0, j = 0) of the H2 molecule, and consequently, those quantities are compared with previous theoretical and experimental results.

47 citations

Journal ArticleDOI
TL;DR: The analysis reveals that nonlinearity present in the system can be instrumental in determining the stability of a system, even to the extent of destabilizing one in a linearly stable parameter regime.
Abstract: We analyze the condition for instability and pattern formation in reaction-diffusion systems beyond the usual linear regime. The approach is based on taking into account perturbations of higher orders. Our analysis reveals that nonlinearity present in the system can be instrumental in determining the stability of a system, even to the extent of destabilizing one in a linearly stable parameter regime. The analysis is also successful to account for the observed effect of additive noise in modifying the instability threshold of a system. The analytical study is corroborated by numerical simulation in a standard reaction-diffusion system.

27 citations

Journal ArticleDOI
TL;DR: A coupled three-dimensional (3D) time-dependent wave packet formalism for the 4D reactive scattering problem in hyperspherical coordinates is implemented on the accurate double many body expansion (DMBE) potential energy surface.
Abstract: We implement a coupled three-dimensional (3D) time-dependent wave packet formalism for the 4D reactive scattering problem in hyperspherical coordinates on the accurate double many body expansion (DMBE) potential energy surface (PES) for the ground and first two singlet states (1(1)A', 2(1)A', and 3(1)A') to account for nonadiabatic processes in the D(+) + H2 reaction for both zero and nonzero values of the total angular momentum (J). As the long-range interactions in D(+) + H2 contribute significantly due to nonadiabatic effects, the convergence profiles of reaction probabilities for the reactive noncharge transfer (RNCT), nonreactive charge transfer (NRCT), and reactive charge transfer (RCT) processes are shown for different collisional energies with respect to the helicity (K) and total angular momentum (J) quantum numbers. The total and state-to-state cross sections are presented as a function of the collision energy for the initial rovibrational state v = 0, j = 0 of the diatom, and the calculated cross sections compared with other theoretical and experimental results.

27 citations

Journal ArticleDOI
TL;DR: A recently proposed coupled three-dimensional time-dependent wave-packet formalism in hyperspherical coordinates is shown to yield accurate results for the reactive non-charge transfer process in the title system at collision energies as low as 100 K.
Abstract: A recently proposed coupled three-dimensional time-dependent wave-packet formalism in hyperspherical coordinates is shown to yield accurate results for the reactive non-charge transfer process in the title system at collision energies as low as 100 K, where the lowest sheet of the accurate double many body expansion form for the singlet H3+ is used. The results are compared with available experimental data as well as time-independent calculations, and the agreement shown to be generally good.

27 citations

Journal ArticleDOI
TL;DR: A coupled three-dimensional (3D) time-dependent wave packet formalism in hyperspherical coordinates for a 4D reactive scattering problem on the lowest adiabatic singlet surface (1(1)A') of the D(+) + H2 reaction.
Abstract: We explore a coupled three-dimensional (3D) time-dependent wave packet formalism in hyperspherical coordinates for a 4D reactive scattering problem on the lowest adiabatic singlet surface (11A′) of...

26 citations


Cited by
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TL;DR: The field of organic electronics has been heavily impacted by the discovery and development of π-conjugated conducting polymers as mentioned in this paper, and polythiophene and its derivatives have been widely investigated computationally and experimentally for use in electronic devices such as light-emitting diodes, water purification devices, hydrogen storage, and biosensors.
Abstract: The field of organic electronics has been heavily impacted by the discovery and development of π-conjugated conducting polymers. These polymers show great potential for integration into future optical and electronic devices due to their capacity to transition between semiconducting and conducting states as well as the ability to alter mechanical properties by controlled doping, chemical modification, and stacking or creating composites with other materials. Among π-conjugated polymers, polythiophene and its derivatives has been one of the most extensively studied and is widely investigated computationally and experimentally for use in electronic devices such as light-emitting diodes, water purification devices, hydrogen storage, and biosensors. Various theoretical modeling studies of polythiophene ranging from an oligothiophene approach to infinite chain lengths (periodic boundary conditions) have been undertaken to study a variety of electronic and structural properties of these polymers. In this review,...

254 citations

Journal ArticleDOI
TL;DR: A rich and varied nano-cluster chemistry for nano-particulate oxides and sulphides, including applications to the widely studied ZnO and ZnS systems, to silica nanochemistry and to group IV oxides including TiO(2).
Abstract: We review the growing role of computational techniques in modelling the structures and properties of nano-particulate oxides and sulphides. We describe the main methods employed, including those based on both electronic structure and interatomic potential approaches. Particular attention is paid to the techniques used in searching for global minima in the energy landscape defined by the nano-particle cluster. We summarise applications to the widely studied ZnO and ZnS systems, to silica nanochemistry and to group IV oxides including TiO2. We also consider the special case of silica cluster chemistry in solution and its importance in understanding the hydrothermal synthesis of microporous materials. The work summarised, together with related experimental studies, demonstrates a rich and varied nano-cluster chemistry for these materials.

179 citations

Journal ArticleDOI
TL;DR: The representative examples selected from recent literature show how broad is the usefulness of this computational method in materials science and related fields.
Abstract: Genetic algorithms (GAs) are a tool used to solve high-complexity computational problems. Apart from modelling the phenomena occurring in Nature, they help in optimization, simulation, modelling, design and prediction purposes in science, medicine, technology, and everyday life. They can be adapted to the given task, be joined with other ones (this leads to combined or hybrid methods), and can work in parallel on many processors. The uses of GAs reported in literature represent a wide variety of approaches and led to solving of numerous computational problems of high complexity. In materials science and related fields of science and technology the GAs open possibilities for materials design, studies of their properties, or production at industrial scale. Here, the recent use of GAs in various domains connected to materials science, solid state physics and chemistry, crystallography, biology, and engineering is reviewed. The listed examples taken from recent literature show how broad the use of these metho...

146 citations