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The present study investigates the electronic band structure and lattice dynamical stability of 2D monolayer sheet of Bi, BiAs and BiSb using density functional theory based on first principles calculation. All these systems are... more
The present study investigates the electronic band structure and lattice dynamical stability of 2D monolayer sheet of Bi, BiAs and BiSb using density functional theory based on first principles calculation. All these systems are semiconductor with direct bandgap. Under tensile strain the bandgap reduces and no bandgap closing is observed upto +5% strain whereas a direct-indirect-metal transition is observed for compressive strain in all these systems. The lattice dynamical stability of these materials has been studied under strain.The present study investigates the electronic band structure and lattice dynamical stability of 2D monolayer sheet of Bi, BiAs and BiSb using density functional theory based on first principles calculation. All these systems are semiconductor with direct bandgap. Under tensile strain the bandgap reduces and no bandgap closing is observed upto +5% strain whereas a direct-indirect-metal transition is observed for compressive strain in all these systems. The lattice dynamical stability of these materials has been studied under strain.
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New colorimetric receptors R1 and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, 1H NMR... more
New colorimetric receptors R1 and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, 1H NMR spectroscopy and mass spectrometry. The receptors R1 and R2 exhibit prominent visual response for F− and AcO– ions allowing the real time analysis of these ions in aqueous media. The formation of the receptor–anion complexes has been supported by UV–vis titration studies and confirmed through binding constant calculations. The anion binding process follows a first order rate equation and the calculated rate constants reveal a higher order of reactivity for AcO− ions. The 1H NMR titration and TDDFT studies provide full support of the binding mechanism. The Hg2+ and F− ion sensing property of receptor R1 has been utilized to arrive at “AND” and “INHIBIT” molecular logic gate applications.
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Scientific Reports 6: Article number: 29309; published online: 07 July 2016; updated: 24 August 2016 The original version of this Article contained a typographical error in the spelling of the author Amitava Banerjee, which was... more
Scientific Reports 6: Article number: 29309; published online: 07 July 2016; updated: 24 August 2016 The original version of this Article contained a typographical error in the spelling of the author Amitava Banerjee, which was incorrectly given as Amitava Banarjee. This has now been corrected in the PDF and HTML versions of the Article.
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In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal... more
In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young’s modulus E, Poisson’s ratio v, shear modulus G, anisotropy factor A and Pugh’s ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory.
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Low temperature calcination methods have been developed to obtain anatase TiO2nanocrystals using three different synthesis routes. The DSC thermograms have been used to set the annealing temperature. Various size of TiO2nanocrystals... more
Low temperature calcination methods have been developed to obtain anatase TiO2nanocrystals using three different synthesis routes. The DSC thermograms have been used to set the annealing temperature. Various size of TiO2nanocrystals ranging from 8 nm to 16.5 nm have been used to synthesize by setting up the annealing temperature and time. The X-ray diffraction (XRD) and Raman spectrum have been used to identify and confirm the anatase crystal structure having long range ordering. The photoluminescence (PL) spectra have been recorded as a function of particle size and excitation power, which is attributed to the defects inside the grain that can migrate into the grain surface region during annealing. In a typical TiO2nanocrystals (sample TN12), luminescence efficiency increases with the decrease in size due to e-/ h+recombination process.
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ABSTRACT The size and shape dependence of mechanical property of metal dioxides MO2 (M = Ti, Sn and Ce) nanowires and nanoparticles with different shapes have been studied using a simple theoretical approach. There is an increase of the... more
ABSTRACT The size and shape dependence of mechanical property of metal dioxides MO2 (M = Ti, Sn and Ce) nanowires and nanoparticles with different shapes have been studied using a simple theoretical approach. There is an increase of the ratio of the Young's modulus at nanoscale to the bulk as size decreases. A good agreement between the present calculated and available theoretical size dependent Young's modulus is found. The Young's modulus is also discussed for different shapes of nanoparticles of metal dioxides and found minimum for the icosahedron shape MO2 nanoparticles.
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Research Interests: Materials Science, Raman Spectroscopy, Vibrational Spectroscopy, Differential scanning calorimetry, Titanium dioxide, and 13 moreThermal Analysis, Analytical Method, Anatase, X ray diffraction, Fourier transform, Differential Scanning Calorimeter, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Thermogravimetric Analysis, Infrared spectra, Porous Material, Fourier transform infrared, and exothermic reaction
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A first principles calculation of the lattice dynamical properties of rutile SnO2 has been performed using density functional perturbation theory at ambient and high‐pressure conditions to understand the pressure‐induced phase transition.... more
A first principles calculation of the lattice dynamical properties of rutile SnO2 has been performed using density functional perturbation theory at ambient and high‐pressure conditions to understand the pressure‐induced phase transition. The calculated zone centre phonon modes at ambient and high pressures have been compared with Raman scattering and infrared measurements. Full phonon dispersion curves and phonon densities of states and Raman intensities at high pressures are calculated and given for the first time in literature. The ferroelastic transition from the rutile to the CaCl2‐type structure was confirmed. It is clearly illustrated that the first transition is associated with macroscopic shear instability which arises from the strong coupling between elastic constants and softening of Raman active B1g mode. The observed pressure of phase transition in experimental measurements was reproduced more accurately than in previous calculations, and the difference between observed...
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Si and Ge nanocrystals (nc-Si and nc-Ge) with average sizes in the range of 6 and 6.3 nm, embedded in SiO2/GeO2 matrix, were fabricated and their acoustic-phonon vibrational properties were investigated using two different approaches by... more
Si and Ge nanocrystals (nc-Si and nc-Ge) with average sizes in the range of 6 and 6.3 nm, embedded in SiO2/GeO2 matrix, were fabricated and their acoustic-phonon vibrational properties were investigated using two different approaches by considering the elastic continuum model and fixed boundary condition. The breathing and quadrupolar modes are found in the spectra. The presence of medium significantly affects the phonon peaks and results into the broadening of the modes which is more in the case of elastically similar materials. The phonon line width is found to depend inversely on the size, similar to that reported experimentally. Using first and second-order optical modes, the electron-phonon coupling strengths have been estimated. The result shows that e-p coupling strength is more in the case of elastically dissimilar materials.
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High phosphorous doped germanium: Dopant diffusion and modeling J. Appl. Phys. 112, 034509 (2012) Understanding Si(111) solid phase epitaxial regrowth using Monte Carlo modeling: Bi-modal growth, defect formation, and interface topology... more
High phosphorous doped germanium: Dopant diffusion and modeling J. Appl. Phys. 112, 034509 (2012) Understanding Si(111) solid phase epitaxial regrowth using Monte Carlo modeling: Bi-modal growth, defect formation, and interface topology J. Appl. Phys. 112, 024327 (2012) Room temperature sub-bandgap photoluminescence from silicon containing oxide precipitates Appl. Phys. Lett. 101, 032107 (2012) Spatial-temporally resolved high-frequency surface acoustic waves on silicon investigated by femtosecond spectroscopy Appl. Phys. Lett. 101, 013108 (2012) Additional information on J. Appl. Phys. Journal Homepage: http://jap.aip.org/ Journal Information: http://jap.aip.org/about/about_the_journal Top downloads: http://jap.aip.org/features/most_downloaded Information for Authors: http://jap.aip.org/authors Si and Ge nanocrystals (nc-Si and nc-Ge) with average sizes in the range of 6 and 6.3 nm, embedded in SiO 2 /GeO 2 matrix, were fabricated and their acoustic-phonon vibrational properties were investigated using two different approaches by considering the elastic continuum model and fixed boundary condition. The breathing and quadrupolar modes are found in the spectra. The presence of medium significantly affects the phonon peaks and results into the broadening of the modes which is more in the case of elastically similar materials. The phonon line width is found to depend inversely on the size, similar to that reported experimentally. Using first and second-order optical modes, the electron-phonon coupling strengths have been estimated. The result shows that e-p coupling strength is more in the case of elastically dissimilar materials.
A first principles calculation of the lattice dynamical properties of rutile SnO 2 has been performed using density functional perturbation theory at ambient and high-pressure conditions to understand the pressure-induced phase... more
A first principles calculation of the lattice dynamical properties of rutile SnO 2 has been performed using density functional perturbation theory at ambient and high-pressure conditions to understand the pressure-induced phase transition. The calculated zone centre phonon modes at ambient and high pressures have been compared with Raman scattering and infrared measurements. Full phonon dispersion curves and phonon densities of states and Raman intensities at high pressures are calculated and given for the first time in literature. The ferroelastic transition from the rutile to the CaCl 2-type structure was confirmed. It is clearly illustrated that the first transition is associated with macroscopic shear instability which arises from the strong coupling between elastic constants and softening of Raman active B 1g mode. The observed pressure of phase transition in experimental measurements was reproduced more accurately than in previous calculations, and the difference between observed and calculated transition pressure is only of the order of 2%. The mode Grüneisen parameter is quantitatively as well as qualitatively different from the earlier reported values.
The present paper reports a study of the influence of heat treatments on the ion-beam synthesis of Si and Ge nanocrystals in SiO 2 layers by low-frequency Raman scattering. Low-frequency Raman scattering is used just because the... more
The present paper reports a study of the influence of heat treatments on the ion-beam synthesis of Si and Ge nanocrystals in SiO 2 layers by low-frequency Raman scattering. Low-frequency Raman scattering is used just because the appearance in the glass matrix of crystal nuclei leads to an additional contribution to the density of only low-frequency acoustic vibrational states due to surface vibration modes of the nuclei. Electron microscopy, contrary to expectations, revealed a decrease rather than increase in the size of the crystal nucleus during annealing. Additionally, low-frequency Raman spectra show that the samples do not have a smooth distribution of nanoparticle sizes, as expected, but two different sizes of Si and Ge nanocrystals. This similarity is surprising because Si and Ge have different diffusion coefficients, temperatures of crystallization, meltings, and binding energies. Despite this, in both cases the same mechanism operates during the growth of Si and Ge nanocrystals.
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Research Interests: Raman Spectroscopy, Vibrational Spectroscopy, Titanium dioxide, Thermal Analysis, Analytical Method, and 8 moreX ray diffraction, Fourier transform, Differential Scanning Calorimeter, Differential Thermal Analysis, Thermogravimetric Analysis, Infrared spectra, Porous Material, and Fourier transform infrared
The present work reports a comprehensive study of structural, dielectric, lattice dynamic and thermo-dynamic properties of magnesium chalcogenides MgX (X ¼ S, Se, and Te) in rock-salt, zinc-blende and wurtzite crystal structures. Density... more
The present work reports a comprehensive study of structural, dielectric, lattice dynamic and thermo-dynamic properties of magnesium chalcogenides MgX (X ¼ S, Se, and Te) in rock-salt, zinc-blende and wurtzite crystal structures. Density functional theory calculations were performed using Perdew-Burke-Ernzerhof (PBE) functional (hereafter, PBE) and along with van der Walls interactions (hereafter, DFT-D). Our calculations show that the inclusion of van der Walls interactions improves the results and predict structural parameters close to the experimental values than using PBE functional alone. Both approaches show that the rock-salt phase is the ground state stable phase of MgS. The DFT-D calculations indicate that rock-salt whereas PBE results show wurtzite as the stable crystal structure for MgSe and MgTe respectively. Further, density functional perturbation theory has been employed to obtain the phonon dispersion curves and phonon density of states. The present phonon calculations show that these compounds are dynamically stable in the three considered phases. Thereafter, temperature dependent heat capacity at constant volume and entropy are also presented and discussed.