Papers by Suman Chowdhury
We investigate the electronic and optical properties of boron-nitrogen pair co-doped 6,6,12-graph... more We investigate the electronic and optical properties of boron-nitrogen pair co-doped 6,6,12-graphyne nanosheets using first-principles calculations. For the electronic band structure, we find the band gap exhibits an even-odd effect with an increase in doping concentration. Exploring the optical properties, we calculate the dielectric function, reflectivity, and absorption coefficient under both parallel and perpendicular polarizations. Remarkably, the co-doped 6,6,12-graphyne shows a broad frequency photoresponse. Under parallel polarizations, co-doping leads to a reduced static dielectric constant in the long wavelength limit. Furthermore, the reflectivity and absorption spectra show that the co-doped 6,6,12graphyne nanosheets are highly sensitive to light from the infrared to the ultraviolet regimes. When doping concentration increases, the maximum reflectivity coefficient increases after an initial decrease under the longitudinal parallel polarization, in contrast to its oscillating behavior under the transverse parallel polarization. For all polarizations, the maximum absorption coefficient varies non-monotonically with doping concentration.
Journal of Physics: Condensed Matter, Mar 27, 2023
Two dimensional transition metal trihalides have drawn attention over the years due to their intr... more Two dimensional transition metal trihalides have drawn attention over the years due to their intrinsic ferromagnetism and associated large anisotropy at nanoscale. The interactions involved in these layered structures are of van der Waals types which are important for exfoliation to different thin samples. This enables one to compare the journey of physical properties from bulk structures to monolayer counterpart. In this topical review, the modulation of electronic, magnetic and optical properties by strain engineering, alloying, doping, defect engineering etc have been discussed extensively. The results obtained by first principle density functional theory calculations are verified by recent experimental observations. The relevant experimental synthesis of different morphological transition metal trihalides are highlighted. The feasibility of such routes may indicate other possible heterostructures. Apart from spintronics based applications, transition metal trihalides are potential candidates in sensing and data storage. Moreover, high thermoelectric figure of merit of chromium trihalides at higher temperatures leads to the possibility of multi-purpose applications. We hope this review will give important directions to further research in transition metal trihalide systems having tunable band gap with reduced dimensionalities.
Applied Surface Science, Nov 1, 2020
Mono and multilayered two dimensional (2D) nitrogene in which nitrogen atoms are single bonded ar... more Mono and multilayered two dimensional (2D) nitrogene in which nitrogen atoms are single bonded are studied for energy applications. The structures are observed to be dynamically and thermally stable at room temperature but dissociate into triple bonded N 2 molecules at higher temperatures. From ab initio molecular dynamics simulations, the dissociation temperature is found to be decreasing with increasing number of layers (1500 K for single layer and 500 K for six layers). The energy released for the different layered cases is large due to the energy difference between single and triple-bonded nitrogen (~0.88-1.8 eV/atom). Significantly high energy densities calculated for the multilayered structures (~6-12.3 kJ/gm) can secure these materials an important position amongst non-nuclear and inorganic high energy density materials known today. We believe that this work will shed light on synthesizing next generation non-nuclear environmentally clean high energy density materials using multi-layer nitrogene that detonate at not very high temperatures.
ACS applied energy materials, Aug 31, 2020
Several selenides have been studied as potential thermoelectric materials in the past. Thermoelec... more Several selenides have been studied as potential thermoelectric materials in the past. Thermoelectric performance improves on reducing the dimension of the system. Following these notions, we studi...
Applied Surface Science, Apr 1, 2022
arXiv (Cornell University), 2015
The main aim of this work is to present two different methodologies for configuration averaging i... more The main aim of this work is to present two different methodologies for configuration averaging in disordered systems. The Recursion method is suitable for the calculation of spatial or self-averaging, while the Augmented space formalism averages over different possible configurations of the system. We have applied these techniques to a simple example and compared their results. Based on these, we have reexamined the concept of spatial ergodicity in disordered systems. The specific aspect, we have focused on, is the question "Why does an experimentalist often obtain the averaged result on a single sample ?" We have found that in our example of disordered graphene, the two lead to the same result within the error limits of the two methods.
Applied Surface Science, Mar 1, 2023
Bulletin of the American Physical Society, 2019
Journal of Physics: Condensed Matter, 2021
In this paper a systematic study is carried out to demonstrate the structural stability and magne... more In this paper a systematic study is carried out to demonstrate the structural stability and magnetic novelty of adsorbing transition metal (TM) dimers (A-B) on graphyne (GY) surface, GY@A-B. Our research points out that the dimers are strongly adsorbed onto GY due to their large natural pores and the electron affinity of the sp-hybridized carbon atoms. Electronic properties of these dimer-graphyne composite systems are of particular importance as they behave as degenerate semiconductors with partial occupation of states at E F. Furthermore, their remarkable spin polarization (>80%) at Fermi energy (E F) can be of paramount importance in spintronics applications. Most of the GY@A-B structures exhibit large magnetic anisotropies as well as magnetic moments along the out-of-plane direction with respect to the GY surface. Particularly, GY@Co–Ir, GY@Ir–Ir and GY@Ir–Os structures possess positive magnetic anisotropic energies (MAE) of 121 meV, 81 meV and 137 meV, respectively, which ar...
Physical Review B, 2021
An unprecedented graphyne allotrope with square symmetry and nodal line semimetallic behavior has... more An unprecedented graphyne allotrope with square symmetry and nodal line semimetallic behavior has been proposed in the two-dimensional (2D) realm. The emergence of the Dirac loop around the high-symmetry points in the presence of both the inversion and time-reversal symmetries is a predominant feature of the electronic band structure of this system. Besides, the structural stability in terms of the dynamic, thermal, and mechanical properties has been critically established for the system. Following the exact analytical model based on the realspace renormalization group scheme and tight-binding approach, we have inferred that the family of 2D nodal line semimetals with square symmetry can be reduced to a universal four-level system in the low-energy limit. This renormalized lattice indeed explains the underlying mechanism responsible for the fascinating emergence of 2D square nodal line semimetals. Besides, the analytical form of the generic dispersion relation of these systems is well supported by our density-functional theory results. Finally, the nontrivial topological properties have been explored for the predicted system without breaking the inversion and time-reversal symmetry of the lattice. We have obtained that the edge states are protected by the nonvanishing topological index, i.e., Zak phase.
Journal of Physics: Condensed Matter, 2019
In the post-graphene era, out of several monolayer 2D materials, Chromium triiodide ([Formula: se... more In the post-graphene era, out of several monolayer 2D materials, Chromium triiodide ([Formula: see text]) has triggered an exotic platform for studying the intrinsic ferromagnetism and large anisotropy at the nanoscale regime. Apart from that, its strong spin-orbit coupling of I also plays a key role in tailoring the electronic properties. In this work, the composition of compressive and tensile strain (uniaxial as well as biaxial) upto 12% have been applied to study the variation of the electronic and magnetic properties of [Formula: see text] employing density functional theory in (LDA+U) exchange correlation scheme. The stability limits of the structures under the influence of strains have been carried out via the deformation potential (DP) and stress-strain relation. For compressive strains in specific directions, the down-spin band gap is seen to be decreasing steadily. The magnetic moment computed from the density of states (DOS) is enhanced significantly under the influence of compressive strain. However, it has been observed that after the application of strain in some specific crystal directions, the magnetic moment of monolayer [Formula: see text] remains almost unchanged. Thus, with the help of strain, the tunning band gap along with underlying characteristic ferromagnetism of this material can unfold a new avenue for potential usage in spintronic devices.
Journal of Magnetism and Magnetic Materials, 2017
The discovery of different two-dimensional (2D) materials both theoretically and experimentally, ... more The discovery of different two-dimensional (2D) materials both theoretically and experimentally, can change the scenario of the current electronic industry because of their intriguing properties. Among the 2D materials, the first one which was discovered experimentally was graphene. In this work we have studied the electronic and magnetic properties of a new allotrope of disordered graphene, which is not hexagonal, rather possesses tetragonal symmetry known as T-graphene (TG). Density functional theory (DFT) has been thoroughly employed to study the relevant electronic properties. In previous works, it has been reported that pristine TG is non-magnetic. It is also known that, introducing transition metal (TM) atoms is a feasible way to control the electronic and magnetic properties. Here we have reported the relevant properties of four TM atoms i.e. Sc, V, Cr and Mn doped TG. From the defect formation energy study, it has been noticed that all the structures are endothermic in nature. For each case, we have found appreciable amount of magnetic moment. With increasing atomic weight of the dopant atom, the magnitude of the magnetic moment also increases. We have tried to explain this magnetic ordering with the help of spin-polarized partial density of states (PDOS). Controlling spin degrees of freedom is important for building spintronic devices. From that point of view, we hope this study will be useful to build TG based spintronic devices.
Journal of Physics and Chemistry of Solids
Physica Scripta
This work reports a detailed and systematic theoretical study of the anisotropic thermoelectric p... more This work reports a detailed and systematic theoretical study of the anisotropic thermoelectric properties of bulk Germanium Sulfide (GeS) in its orthorhombic Pnma phase. Density functional theory (DFT), employing the generalized gradient approximation (GGA), has been used to examine the structural and electronic band structure properties of bulk GeS. Electronic transport properties have been studied by solving semiclassical Boltzmann transport equations. A machine-learning approach has been used to estimate the temperature-dependent lattice part of thermal conductivity. The study reveals that GeS has a direct band gap of 1.20 eV. Lattice thermal conductivity is lowest along crystallographic a-direction, with a minimum of ∼0.98 Wm −1 K −1 at 700 K. We have obtained the maximum figure of merit (ZT) ∼ 0.73 at 700 K and the efficiency ∼7.86% in a working temperature range of 300 K–700 K for pristine GeS along crystallographic a-direction.
Membranes
Ultra-thin diamond membranes, diamanes, are one of the most intriguing quasi-2D films, combining ... more Ultra-thin diamond membranes, diamanes, are one of the most intriguing quasi-2D films, combining unique mechanical, electronic and optical properties. At present, diamanes have been obtained from bi- or few-layer graphene in AA- and AB-stacking by full hydrogenation or fluorination. Here, we study the thermal conductivity of diamanes obtained from bi-layer graphene with twist angle θ between layers forming a Moiré pattern. The combination of DFT calculations and machine learning interatomic potentials makes it possible to perform calculations of the lattice thermal conductivity of such diamanes with twist angles θ of 13.2∘, 21.8∘ and 27.8∘ using the solution of the phonon Boltzmann transport equation. Obtained results show that Moiré diamanes exhibit a wide variety of thermal properties depending on the twist angle, namely a sharp decrease in thermal conductivity from high for “untwisted” diamanes to ultra-low values when the twist angle tends to 30∘, especially for hydrogenated Moi...
Journal of Physics D: Applied Physics
Based upon Hubbard U corrected density functional theory (DFT), the electronic and optical respon... more Based upon Hubbard U corrected density functional theory (DFT), the electronic and optical responses of multiferroic Bismuth ferrite (BiFeO3; BFO) have been critically explored. Treating BFO as a strongly correlated insulating system, a Hubbard U parameter is considered for accurate description of localised Fe-3d states. However, the U parameter for the Fe-3d state is not sufficient as 2p states of O atoms are greatly influenced by Fe-3d states. Similar U parameters for Fe-3d as well as O-2p states are considered. An effective U value around 4.3 eV not only solves the band gap mismatch of BFO from both a theoretical and experimental aspect, but also predicts the exact nature of the band gap. Moreover, within this framework, the optical responses of BFO are critically investigated. Multiple transitions appearing in both theoretical and experimental absorption spectra are well explained by crystal field transitions of Fe3+ ions in a d5 high spin state, supported by the density of stat...
Density Functional Theory, 2018
ACS Applied Materials & Interfaces, 2021
Over the past decade, two-dimensional materials have gained a lot of interest due to their fascin... more Over the past decade, two-dimensional materials have gained a lot of interest due to their fascinating applications in the field of thermoelectricity. In this study, tetragonal monolayers of group-V elements (T-P, T-As, T-Sb, and T-Bi) are systematically analyzed in the framework of density functional theory in combination with the machine-learning approach. The phonon spectra, as well as the strain profile, dictate that these tetragonal structures are geometrically stable as well as they are potential candidates for experimental synthesis. Electronic analysis suggests that tetragonal pnictogens offer a band gap in the semiconducting regime. Thermal transport characteristics are investigated by solving the semiclassical Boltzmann transport equation. Exceptionally low lattice thermal conductivity has been observed as the atomic number increases in the group. The high Seebeck coefficient and electrical conductivity as well as the low thermal conductivity of T-As, T-Sb, and T-Bi lead to the generation of a very high thermoelectric figure of merit as compared to standard thermoelectric materials. Furthermore, the thermoelectric conversion efficiency of these materials has been observed to be much higher, which ensures their implications in thermoelectric device engineering.
Applied Surface Science, 2021
Physical Chemistry Chemical Physics, 2021
The structural, electronic and thermal transport characteristics of novel carbon-based bilayer te... more The structural, electronic and thermal transport characteristics of novel carbon-based bilayer tetragonal graphene are systematically explored with a combination of first-principles calculations and machine-learning interatomic potential approaches.
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Papers by Suman Chowdhury