Bhalchandra S Pujari

Savitribai Phule Pune University | University of Poona · Centre for Modeling and Simulation

According to earlier first-principles calculations, the spin-disorder contribution to the resistivity of rare-earth metals in the paramagnetic state is strongly underestimated if Matthiessen's rule is assumed to hold. To understand this discrepancy, the resistivity of paramagnetic Fe and Gd is evaluated by taking into account both spin and phonon d...

We describe an implementation of the coherent potential approximation within the LMTO formalism, which combines chemical and magnetic disorder treated within the vector disordered local moment model. It allows for arbitrary degree of magnetic order for Heisenberg spins specified by axially symmetric spin distribution functions. The atomic charges a...

We perform a full configuration-interaction study on a square quantum dot containing several electrons in the presence of an attractive impurity. The magnetic ordering in the dot is analyzed using appropriate pair-correlation functions. We find that a change in the size of the quantum dot can change the nature of the impurity from nonmagnetic to ma...

While graphene is a semi-metal, a recently synthesized hydrogenated graphene called graphane is an insulator. We have probed the transformation of graphene upon hydrogenation to graphane within the framework of density functional theory. By analysing the electronic structure for 18 different hydrogen concentrations, we bring out some novel features...

We have carried out ab initio electronic structure calculations on graphane (hydrogenated graphene) with single and double vacancy defects. Our analysis of the density of states reveal that such vacancies induce the mid gap states and modify the band gap. The induced states are due to the unpaired electrons on carbon atoms. Interestingly the placem...

Estimating the burden of COVID-19 in India is difficult because the extent to which cases and deaths have been undercounted is hard to assess. Here, we use a 9-component, age-stratified, contact-structured epidemiological compartmental model, which we call the INDSCI-SIM model, to analyse the first wave of COVID-19 spread in India. We use INDSCI-SI...

ZnO spheres were synthesized by solid state oxidation of ZnS microspheres at different oxidation temperatures of 600 and 700 °C in an ambient atmosphere. The high temperature transformation of ZnS microspheres into hexagonal structured and highly crystalline ZnO microspheres comprising interconnected nanoparticles facilitating efficiently electron...

Assessing the impact of lockdowns on COVID-19 incidence may provide important lessons for management of pandemic in resource-limited settings. We examined growth of incident confirmed COVID-19 patients before, during and after lockdowns during the first wave in Pune city that reported the largest COVID-19 burden at the peak of the pandemic. Using a...

In this work, we investigate the results from the first-principles method based on the electronic structure calculations and study the adsorption properties of CO2 molecule on gallenane (GaH) and sodium decorated gallenane (Na@GaH). The most stable configuration for adsorption on Na@GaH is determined, and the structural parameters, adsorption energ...

Among the lead-free thermoelectric material, germanium telluride (GeTe) has been extensively investigated due to its high thermoelectric performance (ZT) in mid-temperature; however, high p-type carrier density (∼10²¹ cm⁻³) hinder its suitability for higher ZT. In turn, to enhance the thermoelectric performance of the environmentally favorable GeTe...

A systematic analysis of the electronic, thermoelectric and optical properties of triclinic van der Waal's solids NbX2Y2(X = S, Se and Y = Cl, Br, I) is carried out within the framework of density functional theory for bulk and monolayer. The investigated compounds are semiconductors in bulk and monolayer, with band gap values ranging from 1.1 to 1...

We present here the checklist of moths (Lepidoptera: Heterocera) for the campus of Savitribai Phule Pune University, situated in the metropolis of Pune in the state Maharashra in India. We report identification of 189 unique genera along with 154 unique species. Despite the relative small size of the observation area and the location being at the h...

With more than 140 million people infected globally and 3 million deaths, the COVID 19 pandemic has left a lasting impact. A modern response to a pandemic of such proportions needs to focus on exploiting all available data to inform the response in real-time and allow evidence-based decision-making. The intermittent lockdowns in the last 13 months...

Estimating the burden of COVID-19 in India is difficult because the extent to which cases and deaths have been undercounted is hard to assess. The INDSCI-SIM model is a 9-component, age-stratified, contact-structured compartmental model for COVID-19 spread in India. We use INDSCI-SIM, together with Bayesian methods, to obtain optimal fits to report...

Background Real-world data assessing the impact of lockdowns on COVID-19 cases remain limited from resource-limited settings. We examined growth of incident confirmed COVID-19 cases before, during and after lockdowns in Pune, a city in western India with 3.1 million population that reported the largest COVID-19 burden at the peak of the pandemic. M...

We investigate a van der Waals heterostructure constructed using BP and C 3 N and investigate its use as an anode for lithium-, sodium- and potassium-ion batteries.

Using first principles calculations, we investigate the pressure dependent polarization and phase transitions, based on the structural, electronic, piezoelectric and elastic properties in PbTiO3-P4mm, BaTiO3-P4mm, PbZrO3-R3m and BaTiO3-R3m. Under positive pressure, only PbZrO3-R3m does not exhibit a structural phase transition to paraelectric cubic...

The adsorption of molecules NH 3 , CH 4 , and H 2 O are studied on pristine and indium doped phosphorene (In@P). For adsorption, armchair (AC), zigzag, and isotropic/square supercells are used. We have calculated structural, adsorption energies and electronic properties using the first-principles method. The most stable configurations for adsorptio...

The ongoing pandemic of 2019-nCov (COVID-19) coronavirus has made reliable epidemiological modeling an urgent necessity. Unfortunately, most of the existing models are either too fine-grained to be efficient or too coarse-grained to be reliable. Here we propose a computationally efficient hybrid approach that uses SIR model for individual cities wh...

The long spin-diffusion length, spin-lifetimes and excellent optical absorption coefficient of graphene provide an excellent platform for building opto-electronic devices as well as spin-based logic in a nanometer regime. In this study, by employing density functional theory and its time-dependent version, we provide a detailed analysis of how the...

The long spin-diffusion length, spin-lifetimes and excellent optical absorption coefficient of graphene provide an excellent platform for building opto-electronic devices as well as spin-based logic in a nanometer regime. In this study, by employing density functional theory and its time-dependent version, we provide a detailed analysis of how the...

Gallenene (Ga100), a Ga-based 2D material, is a new member of nanomaterial family. Based on the density functional theory (DFT), we studied the adsorption energy, geometry, charge analysis and electronic structure of Na adatom on mono-layer Ga100. Na is an s valence alkali metal. We find the Na atom invoke an affluent diversity of structural, energ...

We studied the structural, energetic and electronic properties of black phosphorene mono layer doped with indium and gallium atom. We replaced a P atom by indium and gallium atom of 16 atom phosphorene mono layer. We found the strong binding of the In and Ga atom with the phosphorene. We suggest that both the atoms are promising dopant. Our results...

We have model the corrugated graphene by applying strain and breaking the symmetry of pure graphene. In the present study, we are not using any substrate. Electronic properties like bandstructure and density of states are studied for corrugated graphene as well as pure graphene. We have not found any opening in band as reported by A. Rossi etal.. W...

Proton conduction ability has been investigated in a new Cu(II) based coordination polymer (CP), {[Cu2(sba)2(bpg)2(H2O)3].5H2O}n (1) synthesized using the combination of 4-sulfobenzoic acid (4-Hsba) and bipyridine-glycoluril (BPG) ligands. Single crystal X-ray structure determination revealed that 1 features 1D porous channels encapsulating a conti...

Bipyridine glycoluril (BPG), a urea-fused bipyridine tecton, forms a square-pyramidal secondary building unit with copper(ii) which further self-assembles to give a porous hydrogen-bonded complex. This complex displays a high proton conductivity of 4.45 × 10-3 S cm-1 at 90 °C and 95% relative humidity (RH). Chains consisting of coordinated water, s...

A first-principles approach to the construction of concentration-temperature magnetic phase diagrams of metallic alloys is presented. The method employs self-consistent total energy calculations based on the coherent potential approximation for partially ordered and noncollinear magnetic states and is able to account for competing interactions and...

Effects of thermal spin disorder and excess Mn on the electronic spectrum of half-metallic NiMnSb are studied using first-principles calculations. Temperature-dependent spin disorder, introduced within the vector disordered local moment model, causes the valence band at the $\Gamma$ point to broaden and shift upwards, crossing the Fermi level and t...

In this work, we have studied the chemical and magnetic interactions of Fe$_n$ ; n=1-6 clusters with vacancy defects (monovacancy to correlated vacancies with six missing C atoms) in a graphene sheet by ab-initio density functional calculations combined with Hubbard U corrections for correlated Fe- d electrons. It is found that the vacancy formatio...

Using the density functional theory we investigate a quasi-two dimensional carbon allotrope, ZzC, formed by square carbon lattice buckled in zigzag manner. By analyzing the Kohn-Sham energy and phonon dispersion obtained by lattice dynamical calculations we show that ZzC is stable with binding energy of 7.46 eV per atom. To examine the possible rou...

We developed a technique to decrease memory requirements when solving the integral equations of three-dimensional (3D) molecular theory of solvation, a.k.a. 3D reference interaction site model (3D-RISM), using the modified direct inversion in the iterative subspace (MDIIS) numerical method of generalized minimal residual type. The latter provides r...

Using density functional theory we investigate a novel carbon allotrope 'SqC': a square planar material that can be more than tetracoordinated. Carbon atoms in this 2D square Bravais lattice form an unusual five-center four-electron bond with neighboring four carbon atoms (tetracoordination). Such an electron-deficient bonding leaves an empty orbit...

The opening of a band gap in graphene through chemical functionalization and realization of nanostructures, is an important issue for technological applications. Using first principles density functional theory, we show that how one can modify the electronic structure of bulk and nanoribbons of graphene by hydrogenation. It is shown that the hydrog...

We study the ground state and excited state geometry, and detailed electronic structure of the germafluorene based polymer PGFDTBT and C 70 interface. The charge transfer is studied by analyzing the charge densities of individual orbitals near the HOMO and LUMO. Our results indicate that the charge transfer at the ground state of Polymer:C 70 inter...

Hydrogenation has proven to be an effective tool to open the bandgap of graphene. In the present density functional study we demonstrate that single-side-hydrogenated graphene is a semiconductor with an indirect bandgap of 1.89 eV, in between the gapless graphene and wide bandgap graphane. We show that its electronic structure and lattice character...

In this work, we have studied the chemical and magnetic interactions of Fe_n; n <= 6, clusters with a divacancy site in a graphene sheet by ab-initio density functional calculations. Our results show significant chemical interactions between the cluster and graphene. As a result, a complex distribution of magnetic moments appear on the distorted Fe...

Grids - the collection of heterogeneous computers spread across the globe - present a new paradigm for the large scale problems in variety of fields. We discuss two representative cases in the area of condensed matter physics outlining the widespread applications of the Grids. Both the problems involve calculations based on commonly used Density Fu...

While graphene is a semi-metal, recently synthesized hydrogenated graphene called graphane, turns out to be an insulator. We have probed the metal insulator Transition in graphene-graphane system within the framework of density functional theory. By analysing the evolutionary trends in the electronic structure for fifteen different hydrogen concent...

Novel extended tetrahedral forms of CO2 have been synthesized recently under high-pressure conditions. We perform ab initio density functional theory calculations to investigate whether doping with Si can extend the stability range of such tetrahedral forms of CO2 to ambient pressure. Calculations are performed with a simple cubic cell containing e...

2, 6, 12, and 20 electron quantum dots have been studied using coupled cluster at singles and doubles level and extensive multireference coupled cluster (MRCC) method. A Fock-space version of MRCC (FSMRCC) containing single hole-particle excited determinants has been used to calculate low-lying excited states of the above system. The ionization pot...

The electronic structure of many-electron square-well quantum dots with and without an attractive impurity has been investigated within the spin-density-functional theory. We consider various sizes of quantum dots with the number of electrons varying from 2 to 20. We observe the emergence of localized Wigner-molecule-like behavior along with the wa...

We reexamine arguments advanced by Hayashi & Matsuda (2001), who claim that several simple, physically motivated derivations based on mean free path theory for calculating the viscous torque in a quasi-Keplerian accretion disk yield results that are inconsistent with the generally accepted model. If correct, the ideas proposed by Hayashi & Matsuda...