| 1. |
- Bandyopadhyay, Arka, et al.
(författare)
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8-16-4 graphyne : Square-lattice two-dimensional nodal line semimetal with a nontrivial topological Zak index
- 2021
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 103:7
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Beer, Tomasz M, et al.
(författare)
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Enzalutamide in metastatic prostate cancer before chemotherapy
- 2014
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Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 371:5, s. 33-424
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Enzalutamide is an oral androgen-receptor inhibitor that prolongs survival in men with metastatic castration-resistant prostate cancer in whom the disease has progressed after chemotherapy. New treatment options are needed for patients with metastatic prostate cancer who have not received chemotherapy, in whom the disease has progressed despite androgen-deprivation therapy.METHODS: In this double-blind, phase 3 study, we randomly assigned 1717 patients to receive either enzalutamide (at a dose of 160 mg) or placebo once daily. The coprimary end points were radiographic progression-free survival and overall survival.RESULTS: The study was stopped after a planned interim analysis, conducted when 540 deaths had been reported, showed a benefit of the active treatment. The rate of radiographic progression-free survival at 12 months was 65% among patients treated with enzalutamide, as compared with 14% among patients receiving placebo (81% risk reduction; hazard ratio in the enzalutamide group, 0.19; 95% confidence interval [CI], 0.15 to 0.23; P<0.001). A total of 626 patients (72%) in the enzalutamide group, as compared with 532 patients (63%) in the placebo group, were alive at the data-cutoff date (29% reduction in the risk of death; hazard ratio, 0.71; 95% CI, 0.60 to 0.84; P<0.001). The benefit of enzalutamide was shown with respect to all secondary end points, including the time until the initiation of cytotoxic chemotherapy (hazard ratio, 0.35), the time until the first skeletal-related event (hazard ratio, 0.72), a complete or partial soft-tissue response (59% vs. 5%), the time until prostate-specific antigen (PSA) progression (hazard ratio, 0.17), and a rate of decline of at least 50% in PSA (78% vs. 3%) (P<0.001 for all comparisons). Fatigue and hypertension were the most common clinically relevant adverse events associated with enzalutamide treatment.CONCLUSIONS: Enzalutamide significantly decreased the risk of radiographic progression and death and delayed the initiation of chemotherapy in men with metastatic prostate cancer. (Funded by Medivation and Astellas Pharma; PREVAIL ClinicalTrials.gov number, NCT01212991.).
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| 3. |
- Chowdhury, Suman, et al.
(författare)
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A real-space study of random extended defects in solids : Application to disordered Stone–Wales defects in graphene
- 2014
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 61:0, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- Abstract We propose here a first-principles, parameter free, real space method for the study of disordered extended defects in solids. We shall illustrate the power of the technique with an application to graphene sheets with randomly placed Stone–Wales defects and shall examine the signature of such random defects on the density of states as a function of their concentration. The technique is general enough to be applied to a whole class of systems with lattice translational symmetry broken not only locally but by extended defects and defect clusters. The real space approach will allow us to distinguish signatures of specific defects and defect clusters.
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| 4. |
- Hazarika, Abhijit, et al.
(författare)
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Ultranarrow and Widely Tunable Mn2+-Induced Photoluminescence from Single Mn-Doped Nanocrystals of ZnS-CdS Alloys
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:26, s. 267401-
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Tidskriftsartikel (refereegranskat)abstract
- Extensively studied Mn-doped semiconductor nanocrystals have invariably exhibited photoluminescence over a narrow energy window of width <= 150 meV in the orange-red region and a surprisingly large spectral width (>= 180 meV), contrary to its presumed atomic-like origin. Carrying out emission measurements on individual single nanocrystals and supported by ab initio calculations, we show that Mn PL emission, in fact, can (i) vary over a much wider range (similar to 370 meV) covering the deep green-deep red region and (ii) exhibit widths substantially lower (similar to 60-75 meV) than reported so far, opening newer application possibilities and requiring a fundamental shift in our perception of the emission from Mn-doped semiconductor nanocrystals.
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| 5. |
- Majumdar, Arnab, et al.
(författare)
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Drastic reduction of thermal conductivity in hexagonal AX (A = Ga, In & Tl, X = S, Se & Te) monolayers due to alternative atomic configuration
- 2021
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 88
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Tidskriftsartikel (refereegranskat)abstract
- Several two-dimensional chalcogenide materials have been in the limelight in the recent past for their promising thermoelectric properties. It is well established that the thermoelectric performance of materials improves on reducing the physical dimensionality of the system. Two-dimensional hexagonal chalcogen (S, Se and Te) bearing compounds of Ga, In and Tl have already been studied extensively in literature. But in those phases, the group-13 non-chalcogen atoms occupy the two inner planes while the chalcogens occupy the two outer planes of the unit cell. In this work, we have proposed the alternate arrangement in which the chalcogen atoms occupy the two inner planes while the group-13 atoms occupy the two outer planes of the unit cell. Unprecedentedly, this alternate arrangement shows much lower thermal conductivity that leads to superior thermoelectric performance. In this work we have studied in details the thermoelectric properties of hexagonal AX (A = Ga, In & Tl, X = S, Se & Te) monolayers and compare the results having both the atomic arrangements. The very low lattice thermal conductivity of this new arrangement is due to the outermost valence s-orbital lone pair of the chalcogens which leads to enhanced anharmonicity. We have explained these results from the anti-crossing of the phonon branches as well. The electronic, dynamical, thermodynamical and elastic properties have also been studied. We think that these results should have significant impact on the synthesis of high-performance thermoelectric materials based on chalcogenides of gallium, indium and thallium.
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| 6. |
- Majumdar, Arnab, et al.
(författare)
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High exothermic dissociation in van der Waals like hexagonal two dimensional nitrogene from first-principles molecular dynamics
- 2020
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 529
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Tidskriftsartikel (refereegranskat)abstract
- 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 (similar to 0.88 - 1.8 eV/atom). Significantly high energy densities calculated for the multilayered structures (similar to 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.
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| 7. |
- Majumdar, Arnab, et al.
(författare)
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Purely ionically bonded cation paving the way to ultralow thermal conductivity and large thermoelectric figure of merit in Ruddlesden-Popper perovskite Cs2SnI2Br2
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 36:34
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Tidskriftsartikel (refereegranskat)abstract
- Lower dimensional materials have gained quite a bit of popularity in the last few decades. Perovskite materials have been studied extensively for their photovoltaic properties. But for large scale application of photovoltaic materials, the thermal properties need to be studied. In this work, using first principles calculations, we have studied the thermal conductivity and thermoelectric performance of quasi two-dimensional (2D) Ruddlesden-Popper phase of perovskite, Cs2SnI2Br2. The Cs atoms are found to be ionically bonded to the halogens leading to low elastic constants and hence give rise to weak bonding. The large anharmonicity in this material causes the lattice thermal conductivity to be ultralow having a value of 0.30 Wm(-1)K-1 at 300 K and therefore the thermoelectric figure of merit has been found to be high with a maximum value of 2.08 at 600 K. This lead-free 2D perovskite can be the precursor to a wide variety of similar materials with ultralow thermal conductivity.
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| 8. |
- Majumdar, Arnab, et al.
(författare)
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Ultralow Thermal Conductivity and High Thermoelectric Figure of Merit in Two-Dimensional Thallium Selenide
- 2020
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:9, s. 9315-9325
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Tidskriftsartikel (refereegranskat)abstract
- 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 studied three hexagonal two-dimensional phases of thallium selenide for promising thermoelectric performance by using first-principles techniques. Their dynamical and mechanical stabilities have been shown. The band gaps using different approximations of calculations have been reported and are in the range that can render these materials to show optimal thermoelectric performance. The lattice thermal conductivity is ultralow between 0.088 and 0.429 W m(-1) K-1 at 900 K. High thermoelectric performance has been predicted in the systems with the figure of merit reaching magnitudes of similar to 0.5-1.94 between 300 and 900 K. The high thermoelectric performance results from an ultralow thermal conductivity arising due to the strong lattice anharmonicity. These results can have significant impact on the synthesis of high performance thermoelectric materials based on thallium selenide.
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