Swapan Ghosh - Academia.edu (original) (raw)

Papers by Swapan Ghosh

Research paper thumbnail of Position-Dependent Diffusion induced Non-monotonic decay of Certain Non-Equilibrium Phenomena in Condensed Phase

The dynamics of various optically controlled non-equilibrium phenomena in the condensed phase are... more The dynamics of various optically controlled non-equilibrium phenomena in the condensed phase are studied using the Liouville equation. We study a projection of the same in a slow moving coordinate, identified as the Reaction Coordinate approach, with a position dependent diffusion coefficient. Introduction of position dependence is shown to induce non-monotonicity in relaxations of certain Non-equilibrium correlation functions, previously unexplored in the theoretical as well as experimental studies. This is in contrast to the exponential relaxation of its position independent analogue, irrespective of initial conditions. We characterize the dependence of this non-monotonicity on the strength of spatial inhomogeneity of diffusion and on the strength of the restoring forces and also indicate ranges of combinations where this feature is exhibited to pave the way for its experimental detection.

Research paper thumbnail of www.mdpi.org/ijms/ Density Functional Theory and Materials Modeling at Atomistic Length Scales

Abstract: We discuss the basic concepts of density functional theory (DFT) as applied to material... more Abstract: We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT consists of Boltzmann type distributions, both corresponding to a system of noninteracting particles in the field of a density-dependent effective potential, the exact functional form of which is unknown. One therefore approximates the exchange-correlation potential for quantum systems and the excess free energy density functional or the direct correlation functions for classical systems. Illustrative applications of quantum DFT to microscopic modeling of molecular interaction and that of classical DFT to a mesoscopic modeling of soft condensed matter systems are highlighted.

Research paper thumbnail of A Path Integral approach to Quantum Fluid Dynamics

arXiv: Quantum Physics, 2020

In this work we develop a new alternative approach towards solutions of Quantum Trajectories, wit... more In this work we develop a new alternative approach towards solutions of Quantum Trajectories, within the framework of quantum fluid dynamics (QFD), using the Path Integral method. The state-of-the-art technique in the field is to solve the non-linear, coupled partial differential equations (PDEs) simultaneously. We, however opt for a fundamentally different route, by first developing a formal closed form expression for the Path Integral propagator as a functional of the classical path. The method is exact and is applicable in many dimensions as well as multi-particle cases. This, then, is used to compute the Quantum Potential, which, in turn, can generate Quantum Trajectories. For cases, where closed form solution is not possible, the problem is boiled down to solving the classical path (linear time complexity) as a boundary value problem. The work formally bridges the Path Integral approach with Quantum Fluid Dynamics. As a model application to illustrate the method, we work out a ...

Research paper thumbnail of Photocatalytic splitting of water on s-triazine based graphitic carbon nitride: an ab initio investigation

Journal of Materials Chemistry A, 2015

Ab initio investigations have been carried out to understand the mechanism of photocatalytic wate... more Ab initio investigations have been carried out to understand the mechanism of photocatalytic water splitting on a g-CN based semiconductor photocatalyst.

Research paper thumbnail of Density Functional Theory and Materials Modeling at Atomistic Length Scales

International Journal of Molecular Sciences, 2002

We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling... more We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT consists of Boltzmann type distributions, both corresponding to a system of noninteracting particles in the field of a density-dependent effective potential, the exact functional form of which is unknown. One therefore approximates the exchange-correlation potential for quantum systems and the excess free energy density functional or the direct correlation functions for classical systems. Illustrative applications of quantum DFT to microscopic modeling of molecular interaction and that of classical DFT to a mesoscopic modeling of soft condensed matter systems are highlighted.

Research paper thumbnail of Study of correlation effects in an exactly solvable model two‐electron system

The Journal of Chemical Physics, 1991

ABSTRACT

Research paper thumbnail of Quantum Fluid Dynamics from Path Integrals

In this work, we develop analytical solutions to the general problem of computing Quantum Traject... more In this work, we develop analytical solutions to the general problem of computing Quantum Trajectories, within the framework of quantum fluid dynamics (QFD). The state-of-the-art technique in the field is to simultaneously solve the non-linear, coupled partial differential equations (PDEs) numerically. We, however, set off from Feynman Path Integrals, and analytically compute the propagator for a general system. This, then, is used to compute the Quantum Potential, which can generate Quantum Trajectories. For cases, where a closed-form solution is not possible, the problem is shown to be reducible to a single real-valued numerical integration (linear time complexity). The work formally bridges the Path Integral approach with Quantum Fluid Dynamics. As a model application to illustrate the method, we solve for the Quantum Potential of Quartic Anharmonic Oscillator and delve into seeking insight into one of the long-standing debates with regard to Quantum Tunneling.

Research paper thumbnail of Hypervirial theorems and scaling relations in density functional theory

A is shown to be given by ∫dr ρ(r) 1/2 [μ, ˆ A ] ρ(r) 1/2 = 0, where ρ(r) is the single particle ... more A is shown to be given by ∫dr ρ(r) 1/2 [μ, ˆ A ] ρ(r) 1/2 = 0, where ρ(r) is the single particle electron density of a many-electron system. The chemical potential operator μ expressed as either a multiplicative or a differential operator, depending on the variant of DFT, is shown to yield equivalent results. The consequence of using approximate forms of the energy density functionals are discussed and for special cases of the operator ˆ A , the virial theorem in DFT is recovered. Generalised scaling relations for the energy density functionals are obtained and the implications towards tensor virial theorem are discussed.

Research paper thumbnail of Chemical Binding and Reactivity Parameters: A Unified Coarse Grained Density Functional View

Chemical Reactivity in Confined Systems

Research paper thumbnail of Alkali-metal-induced enhancement of hydrogen adsorption in C60 fullerene: an ab Initio study

Nano letters, 2008

It is demonstrated that the doping of alkali metal atoms on fullerene, C60, remarkably enhances t... more It is demonstrated that the doping of alkali metal atoms on fullerene, C60, remarkably enhances the molecular hydrogen adsorption capacity of fullerenes, which is higher than that of conventionally known other fullerene complexes. This effect is observed to be more ...

Research paper thumbnail of Exploring triazine and heptazine based self assembled molecular materials through first principles investigations

Journal of Molecular Modeling

Research paper thumbnail of Molecular softness as the average of atomic softnesses: companion principle to the geometric mean principle for electronegativity equalization

The Journal of Physical Chemistry

... Weitao Yang,* Chengteh Lee, and Swapan K. Ghosht Department of Chemistry, University of North... more ... Weitao Yang,* Chengteh Lee, and Swapan K. Ghosht Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 2751 4 (Received: July 25, 1985) ... Chem. SOC., 106, 4049 (1984). (5) W. Yang, RG Parr, and R. Pucci, J. Chem. Phys., 81,2862 (1984). ...

Research paper thumbnail of Porous Graphitic Carbon Nitride: A Possible Metal-free Photocatalyst for Water Splitting

The Journal of Physical Chemistry C

Research paper thumbnail of A computational investigation of the red and blue shifts in hydrogen bonded systems

Journal of Chemical Sciences

The present work reports results of computational investigations of hydrogen bonding, with regard... more The present work reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters are proposed, thereby generating new insight into both types of the frequency shifts. Thus, the frequency shifts in X-H-Y hydrogen bonded systems at different H-Y distances are shown to correlate well with the Mulliken charges on H and Y, with the positive and negative charges on Y correlating with the blue and red shift of the frequency of X-H vibration, respectively. The role played by charge transfers at other parts of the interacting system is also discussed.

Research paper thumbnail of Improvement of photocatalytic activity of NaTaO 3 under visible light by N and F doping

Chemical Physics Letters

ABSTRACT In this study, a systematic quantum chemical calculation has been performed to investiga... more ABSTRACT In this study, a systematic quantum chemical calculation has been performed to investigate the synergistic effect of N and F doping on the photocatalytic properties of NaTaO3. The doping approach is found to be successful in extending the absorption curve of NaTaO3 toward the visible region. The presence of F not only passivates N-induced unoccupied midgap states but also facilitates the introduction of N by reducing the formation energy significantly. The band edge positions for the (N, F)-codoped NaTaO3 with respect to water redox levels are such that it can be a potential photocatalyst for overall water splitting.

Research paper thumbnail of An Efficient Strategy for Controlled Band Gap Engineering of KTaO3

The Journal of Physical Chemistry C

Research paper thumbnail of Role of F in Improving the Photocatalytic Activity of Rh-Doped SrTiO3

The Journal of Physical Chemistry C

ABSTRACT In this study, the effect of F doping on the electronic structure and photocatalytic act... more ABSTRACT In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh-doped SrTiO3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photo-conversion efficiency has been found to be poor. This is due to Rh+4 state, which introduces localized unoccupied states above the valence band and promotes the electron-hole recombination process. Upon codoping with F, the localized states are found to be completely passivated. Analysis of Bader charge indicates the existence of lower oxidation state of Rh in the (Rh, F)-codoped SrTiO3. The valence band maxima is elevated significantly due to strong hybridization of O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of band structure of (Rh, F)-codoped SrTiO3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results into a clean band structure but also reduces the band gap by a larger extent (0.88 eV). In the case of 2:1 (Rh, F)-codoping, localized unoccupied states in the forbidden region are still present. Calculation of the defect formation energy indicates that the doping of Rh becomes more feasible in presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F)-codoped SrTiO3 are found to be suitable for the overall water splitting process. Hence, introduction of F is expected to enhance the photocatalytic activity of Rh-doped SrTiO3 under visible light due to narrowing of the band gap as well as lowering of electron-hole recombination rate.

Research paper thumbnail of Improving the photocatalytic activity of s-triazine based graphitic carbon nitride through metal decoration: an ab initio investigation

Physical chemistry chemical physics : PCCP, Jan 29, 2016

Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts f... more Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts for generating hydrogen through solar water splitting. Through more accurate hybrid density functional theory calculations, we attempted to tune the electronic band structure of poly s-triazine based graphitic carbon nitride by decorating it with different metal atoms and clusters for improving its visible light absorption efficiency. For deposition on the two-dimensional carbon nitride surface, a range of metals have been considered which include all the 3d transition metals and the noble metals (Ag, Au, Pt and Pd). Our study reveals that though the band gaps of all the metal decorated systems were less than that of pristine carbon nitride, in most of the cases, metal decoration leads to the formation of mid gap impurity states, which can hinder the mobility of charge carriers. However, in the case of Ag and its four atom cluster deposited systems, no mid gap states were observed. In all...

Research paper thumbnail of Study of Correlation Effects in an Exactly Solvable Model Two-Electron System

The Journal of Chemical Physics, 1991

ABSTRACT

Research paper thumbnail of Modified weighted density-functional approach to the crystal-melt interface

Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Feb 1, 1998

ABSTRACT

Research paper thumbnail of Position-Dependent Diffusion induced Non-monotonic decay of Certain Non-Equilibrium Phenomena in Condensed Phase

The dynamics of various optically controlled non-equilibrium phenomena in the condensed phase are... more The dynamics of various optically controlled non-equilibrium phenomena in the condensed phase are studied using the Liouville equation. We study a projection of the same in a slow moving coordinate, identified as the Reaction Coordinate approach, with a position dependent diffusion coefficient. Introduction of position dependence is shown to induce non-monotonicity in relaxations of certain Non-equilibrium correlation functions, previously unexplored in the theoretical as well as experimental studies. This is in contrast to the exponential relaxation of its position independent analogue, irrespective of initial conditions. We characterize the dependence of this non-monotonicity on the strength of spatial inhomogeneity of diffusion and on the strength of the restoring forces and also indicate ranges of combinations where this feature is exhibited to pave the way for its experimental detection.

Research paper thumbnail of www.mdpi.org/ijms/ Density Functional Theory and Materials Modeling at Atomistic Length Scales

Abstract: We discuss the basic concepts of density functional theory (DFT) as applied to material... more Abstract: We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT consists of Boltzmann type distributions, both corresponding to a system of noninteracting particles in the field of a density-dependent effective potential, the exact functional form of which is unknown. One therefore approximates the exchange-correlation potential for quantum systems and the excess free energy density functional or the direct correlation functions for classical systems. Illustrative applications of quantum DFT to microscopic modeling of molecular interaction and that of classical DFT to a mesoscopic modeling of soft condensed matter systems are highlighted.

Research paper thumbnail of A Path Integral approach to Quantum Fluid Dynamics

arXiv: Quantum Physics, 2020

In this work we develop a new alternative approach towards solutions of Quantum Trajectories, wit... more In this work we develop a new alternative approach towards solutions of Quantum Trajectories, within the framework of quantum fluid dynamics (QFD), using the Path Integral method. The state-of-the-art technique in the field is to solve the non-linear, coupled partial differential equations (PDEs) simultaneously. We, however opt for a fundamentally different route, by first developing a formal closed form expression for the Path Integral propagator as a functional of the classical path. The method is exact and is applicable in many dimensions as well as multi-particle cases. This, then, is used to compute the Quantum Potential, which, in turn, can generate Quantum Trajectories. For cases, where closed form solution is not possible, the problem is boiled down to solving the classical path (linear time complexity) as a boundary value problem. The work formally bridges the Path Integral approach with Quantum Fluid Dynamics. As a model application to illustrate the method, we work out a ...

Research paper thumbnail of Photocatalytic splitting of water on s-triazine based graphitic carbon nitride: an ab initio investigation

Journal of Materials Chemistry A, 2015

Ab initio investigations have been carried out to understand the mechanism of photocatalytic wate... more Ab initio investigations have been carried out to understand the mechanism of photocatalytic water splitting on a g-CN based semiconductor photocatalyst.

Research paper thumbnail of Density Functional Theory and Materials Modeling at Atomistic Length Scales

International Journal of Molecular Sciences, 2002

We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling... more We discuss the basic concepts of density functional theory (DFT) as applied to materials modeling in the microscopic, mesoscopic and macroscopic length scales. The picture that emerges is that of a single unified framework for the study of both quantum and classical systems. While for quantum DFT, the central equation is a one-particle Schrodinger-like Kohn-Sham equation, the classical DFT consists of Boltzmann type distributions, both corresponding to a system of noninteracting particles in the field of a density-dependent effective potential, the exact functional form of which is unknown. One therefore approximates the exchange-correlation potential for quantum systems and the excess free energy density functional or the direct correlation functions for classical systems. Illustrative applications of quantum DFT to microscopic modeling of molecular interaction and that of classical DFT to a mesoscopic modeling of soft condensed matter systems are highlighted.

Research paper thumbnail of Study of correlation effects in an exactly solvable model two‐electron system

The Journal of Chemical Physics, 1991

ABSTRACT

Research paper thumbnail of Quantum Fluid Dynamics from Path Integrals

In this work, we develop analytical solutions to the general problem of computing Quantum Traject... more In this work, we develop analytical solutions to the general problem of computing Quantum Trajectories, within the framework of quantum fluid dynamics (QFD). The state-of-the-art technique in the field is to simultaneously solve the non-linear, coupled partial differential equations (PDEs) numerically. We, however, set off from Feynman Path Integrals, and analytically compute the propagator for a general system. This, then, is used to compute the Quantum Potential, which can generate Quantum Trajectories. For cases, where a closed-form solution is not possible, the problem is shown to be reducible to a single real-valued numerical integration (linear time complexity). The work formally bridges the Path Integral approach with Quantum Fluid Dynamics. As a model application to illustrate the method, we solve for the Quantum Potential of Quartic Anharmonic Oscillator and delve into seeking insight into one of the long-standing debates with regard to Quantum Tunneling.

Research paper thumbnail of Hypervirial theorems and scaling relations in density functional theory

A is shown to be given by ∫dr ρ(r) 1/2 [μ, ˆ A ] ρ(r) 1/2 = 0, where ρ(r) is the single particle ... more A is shown to be given by ∫dr ρ(r) 1/2 [μ, ˆ A ] ρ(r) 1/2 = 0, where ρ(r) is the single particle electron density of a many-electron system. The chemical potential operator μ expressed as either a multiplicative or a differential operator, depending on the variant of DFT, is shown to yield equivalent results. The consequence of using approximate forms of the energy density functionals are discussed and for special cases of the operator ˆ A , the virial theorem in DFT is recovered. Generalised scaling relations for the energy density functionals are obtained and the implications towards tensor virial theorem are discussed.

Research paper thumbnail of Chemical Binding and Reactivity Parameters: A Unified Coarse Grained Density Functional View

Chemical Reactivity in Confined Systems

Research paper thumbnail of Alkali-metal-induced enhancement of hydrogen adsorption in C60 fullerene: an ab Initio study

Nano letters, 2008

It is demonstrated that the doping of alkali metal atoms on fullerene, C60, remarkably enhances t... more It is demonstrated that the doping of alkali metal atoms on fullerene, C60, remarkably enhances the molecular hydrogen adsorption capacity of fullerenes, which is higher than that of conventionally known other fullerene complexes. This effect is observed to be more ...

Research paper thumbnail of Exploring triazine and heptazine based self assembled molecular materials through first principles investigations

Journal of Molecular Modeling

Research paper thumbnail of Molecular softness as the average of atomic softnesses: companion principle to the geometric mean principle for electronegativity equalization

The Journal of Physical Chemistry

... Weitao Yang,* Chengteh Lee, and Swapan K. Ghosht Department of Chemistry, University of North... more ... Weitao Yang,* Chengteh Lee, and Swapan K. Ghosht Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 2751 4 (Received: July 25, 1985) ... Chem. SOC., 106, 4049 (1984). (5) W. Yang, RG Parr, and R. Pucci, J. Chem. Phys., 81,2862 (1984). ...

Research paper thumbnail of Porous Graphitic Carbon Nitride: A Possible Metal-free Photocatalyst for Water Splitting

The Journal of Physical Chemistry C

Research paper thumbnail of A computational investigation of the red and blue shifts in hydrogen bonded systems

Journal of Chemical Sciences

The present work reports results of computational investigations of hydrogen bonding, with regard... more The present work reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters are proposed, thereby generating new insight into both types of the frequency shifts. Thus, the frequency shifts in X-H-Y hydrogen bonded systems at different H-Y distances are shown to correlate well with the Mulliken charges on H and Y, with the positive and negative charges on Y correlating with the blue and red shift of the frequency of X-H vibration, respectively. The role played by charge transfers at other parts of the interacting system is also discussed.

Research paper thumbnail of Improvement of photocatalytic activity of NaTaO 3 under visible light by N and F doping

Chemical Physics Letters

ABSTRACT In this study, a systematic quantum chemical calculation has been performed to investiga... more ABSTRACT In this study, a systematic quantum chemical calculation has been performed to investigate the synergistic effect of N and F doping on the photocatalytic properties of NaTaO3. The doping approach is found to be successful in extending the absorption curve of NaTaO3 toward the visible region. The presence of F not only passivates N-induced unoccupied midgap states but also facilitates the introduction of N by reducing the formation energy significantly. The band edge positions for the (N, F)-codoped NaTaO3 with respect to water redox levels are such that it can be a potential photocatalyst for overall water splitting.

Research paper thumbnail of An Efficient Strategy for Controlled Band Gap Engineering of KTaO3

The Journal of Physical Chemistry C

Research paper thumbnail of Role of F in Improving the Photocatalytic Activity of Rh-Doped SrTiO3

The Journal of Physical Chemistry C

ABSTRACT In this study, the effect of F doping on the electronic structure and photocatalytic act... more ABSTRACT In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh-doped SrTiO3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photo-conversion efficiency has been found to be poor. This is due to Rh+4 state, which introduces localized unoccupied states above the valence band and promotes the electron-hole recombination process. Upon codoping with F, the localized states are found to be completely passivated. Analysis of Bader charge indicates the existence of lower oxidation state of Rh in the (Rh, F)-codoped SrTiO3. The valence band maxima is elevated significantly due to strong hybridization of O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of band structure of (Rh, F)-codoped SrTiO3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results into a clean band structure but also reduces the band gap by a larger extent (0.88 eV). In the case of 2:1 (Rh, F)-codoping, localized unoccupied states in the forbidden region are still present. Calculation of the defect formation energy indicates that the doping of Rh becomes more feasible in presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F)-codoped SrTiO3 are found to be suitable for the overall water splitting process. Hence, introduction of F is expected to enhance the photocatalytic activity of Rh-doped SrTiO3 under visible light due to narrowing of the band gap as well as lowering of electron-hole recombination rate.

Research paper thumbnail of Improving the photocatalytic activity of s-triazine based graphitic carbon nitride through metal decoration: an ab initio investigation

Physical chemistry chemical physics : PCCP, Jan 29, 2016

Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts f... more Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts for generating hydrogen through solar water splitting. Through more accurate hybrid density functional theory calculations, we attempted to tune the electronic band structure of poly s-triazine based graphitic carbon nitride by decorating it with different metal atoms and clusters for improving its visible light absorption efficiency. For deposition on the two-dimensional carbon nitride surface, a range of metals have been considered which include all the 3d transition metals and the noble metals (Ag, Au, Pt and Pd). Our study reveals that though the band gaps of all the metal decorated systems were less than that of pristine carbon nitride, in most of the cases, metal decoration leads to the formation of mid gap impurity states, which can hinder the mobility of charge carriers. However, in the case of Ag and its four atom cluster deposited systems, no mid gap states were observed. In all...

Research paper thumbnail of Study of Correlation Effects in an Exactly Solvable Model Two-Electron System

The Journal of Chemical Physics, 1991

ABSTRACT

Research paper thumbnail of Modified weighted density-functional approach to the crystal-melt interface

Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Feb 1, 1998

ABSTRACT