Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1360461
Md. Ibrahim Kholil, Md. Shahinur Islam, M. A. Rahman
Abstract Structural, elastic, electronic, optical, thermodynamic, and superconducting properties of the Laves phase superconductor LaRu2 with Tc ~ 1.63 K were investigated using the first-principles calculations for the first time. The corresponding evaluated structural parameters are in good agreement with the available theoretical values. The different elastic properties like as, elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν were calculated using the Voigt–Reuss–Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh’s ratio. The band structure and Cauchy pressure shows that the material behaves metallic nature. The calculated total density of state is 6.80 (electrons/eV) of LaRu2. The optical properties such as reflectivity, absorption spectrum, refractive index, dielectric function, conductivity, and energy loss spectrum are also calculated. The photoconductivity reveals the metallic nature of LaRu2 and absorption coefficient is good in the infrared region. The evaluated density and Debye temperature are 9.55 gm/cm3 and 110.51 K, respectively. In addition, the study of thermodynamic properties like as minimum thermal conductivity, melting temperature, and Dulong–Petit limit are 0.26 (Wm−1 K−1), 1,471.65 K, and 74.80 (J/mole K), respectively. Finally, the investigated electron-phonon coupling constant is 0.66 of LaRu2 superconductor.
{"title":"Ab-initio study of C15-type Laves phase superconductor LaRu2","authors":"Md. Ibrahim Kholil, Md. Shahinur Islam, M. A. Rahman","doi":"10.1080/23311940.2017.1360461","DOIUrl":"https://doi.org/10.1080/23311940.2017.1360461","url":null,"abstract":"Abstract Structural, elastic, electronic, optical, thermodynamic, and superconducting properties of the Laves phase superconductor LaRu2 with Tc ~ 1.63 K were investigated using the first-principles calculations for the first time. The corresponding evaluated structural parameters are in good agreement with the available theoretical values. The different elastic properties like as, elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν were calculated using the Voigt–Reuss–Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh’s ratio. The band structure and Cauchy pressure shows that the material behaves metallic nature. The calculated total density of state is 6.80 (electrons/eV) of LaRu2. The optical properties such as reflectivity, absorption spectrum, refractive index, dielectric function, conductivity, and energy loss spectrum are also calculated. The photoconductivity reveals the metallic nature of LaRu2 and absorption coefficient is good in the infrared region. The evaluated density and Debye temperature are 9.55 gm/cm3 and 110.51 K, respectively. In addition, the study of thermodynamic properties like as minimum thermal conductivity, melting temperature, and Dulong–Petit limit are 0.26 (Wm−1 K−1), 1,471.65 K, and 74.80 (J/mole K), respectively. Finally, the investigated electron-phonon coupling constant is 0.66 of LaRu2 superconductor.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1360461","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42307780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1361077
M. Tassi, A. Morphis, K. Lambropoulos, C. Simserides
Abstract We employ Real-Time Time-Dependent Density Functional Theory to study hole oscillations within a B-DNA monomer (one base pair) or dimer (two base pairs). Placing the hole initially at any of the bases which make up a base pair, results in THz oscillations, albeit of negligible amplitude. Placing the hole initially at any of the base pairs which make up a dimer is more interesting: For dimers made of identical monomers, we predict oscillations with frequencies in the range 20–40 THz, with a maximum transfer percentage close to 1. For dimers made of different monomers, 80–400 THz, but with very small or small maximum transfer percentage. We compare our results with those obtained recently via our Tight-Binding approaches and find that they are in good agreement.
{"title":"RT-TDDFT study of hole oscillations in B-DNA monomers and dimers","authors":"M. Tassi, A. Morphis, K. Lambropoulos, C. Simserides","doi":"10.1080/23311940.2017.1361077","DOIUrl":"https://doi.org/10.1080/23311940.2017.1361077","url":null,"abstract":"Abstract We employ Real-Time Time-Dependent Density Functional Theory to study hole oscillations within a B-DNA monomer (one base pair) or dimer (two base pairs). Placing the hole initially at any of the bases which make up a base pair, results in THz oscillations, albeit of negligible amplitude. Placing the hole initially at any of the base pairs which make up a dimer is more interesting: For dimers made of identical monomers, we predict oscillations with frequencies in the range 20–40 THz, with a maximum transfer percentage close to 1. For dimers made of different monomers, 80–400 THz, but with very small or small maximum transfer percentage. We compare our results with those obtained recently via our Tight-Binding approaches and find that they are in good agreement.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1361077","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43397535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1412107
Kevin M. Hope, G. Samudrala, Y. Vohra
Abstract The atomic volume of rare earth metal dysprosium (Dy) has been measured up to high pressures of 35 GPa and low temperatures between 200 and 7 K in a diamond anvil cell using angle dispersive X-ray diffraction at a synchrotron source. The hexagonal close-packed (hcp), alpha-Samarium (α-Sm), and double hexagonal close-packed (dhcp) phases are observed to be stable in Dy under high-pressure and low-temperature conditions achieved in our experiments. Dy is known to undergo magnetic ordering below 176 K at ambient pressure with magnetic ordering Néel temperature (TN) that changes rapidly with increasing pressure. Our experimental measurement shows that Dy has near-zero thermal expansion in the magnetically ordered state and normal thermal expansion in the paramagnetic state for all the three known high pressure phases (hcp, α-Sm, and dhcp) to 35 GPa. This near-zero thermal expansion behavior in Dy is observed below the magnetic ordering temperature TN at all pressures up to 35 GPa.
{"title":"Near-zero thermal expansion in magnetically ordered state in dysprosium at high pressures and low temperatures","authors":"Kevin M. Hope, G. Samudrala, Y. Vohra","doi":"10.1080/23311940.2017.1412107","DOIUrl":"https://doi.org/10.1080/23311940.2017.1412107","url":null,"abstract":"Abstract The atomic volume of rare earth metal dysprosium (Dy) has been measured up to high pressures of 35 GPa and low temperatures between 200 and 7 K in a diamond anvil cell using angle dispersive X-ray diffraction at a synchrotron source. The hexagonal close-packed (hcp), alpha-Samarium (α-Sm), and double hexagonal close-packed (dhcp) phases are observed to be stable in Dy under high-pressure and low-temperature conditions achieved in our experiments. Dy is known to undergo magnetic ordering below 176 K at ambient pressure with magnetic ordering Néel temperature (TN) that changes rapidly with increasing pressure. Our experimental measurement shows that Dy has near-zero thermal expansion in the magnetically ordered state and normal thermal expansion in the paramagnetic state for all the three known high pressure phases (hcp, α-Sm, and dhcp) to 35 GPa. This near-zero thermal expansion behavior in Dy is observed below the magnetic ordering temperature TN at all pressures up to 35 GPa.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1412107","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44532402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1357325
Wenbin Lin
Abstract Birkhoff’s theorem states that the external gravitational field of any spherically-symmetric system is static and is described by Schwarzschild metric. In this paper, we demonstrate that it is inconsistent with the direct post-Newtonian solution to Einstein field equations in the weak field limit. Moreover, we identify the flaw in the derivation of Birkhoff’s theorem—the consequences of making the coordinate transformations for solving Einstein field equations are ignored, which is due to the misuse of the covariance in general relativity.
{"title":"Does Birkhoff’s theorem really hold?","authors":"Wenbin Lin","doi":"10.1080/23311940.2017.1357325","DOIUrl":"https://doi.org/10.1080/23311940.2017.1357325","url":null,"abstract":"Abstract Birkhoff’s theorem states that the external gravitational field of any spherically-symmetric system is static and is described by Schwarzschild metric. In this paper, we demonstrate that it is inconsistent with the direct post-Newtonian solution to Einstein field equations in the weak field limit. Moreover, we identify the flaw in the derivation of Birkhoff’s theorem—the consequences of making the coordinate transformations for solving Einstein field equations are ignored, which is due to the misuse of the covariance in general relativity.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1357325","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48001951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1354957
F. Caridi, G. Belmusto
Abstract Wild-growing mushrooms are a complementary foodstuff, widely consumed as a delicacy, in Italy. They are considered excellent bioindicators of environmental pollution and the accumulation of radionuclides can pose a radiological hazard. 137Cs and 40K activity concentrations were measured through HPGe gamma-spectrometry in different mushroom species (Agaricus arvensis, Leccinum quercinum, Boletus aereus, Lactarius deliciosus, Boletus edulis, Macrolepiota konradii, Cantharellus lutescens) collected from four different sampling sites in the Calabria region, south of Italy. Experimental values were found to be in the range from (0.3 ± 0.1) Bq/kg f.m. (fresh mass) to (73.1 ± 4.6) Bq/kg f.m. for 137Cs and from (46.9 ± 10.7) Bq/kg f.m. to (161.3 ± 12.9) Bq/kg f.m. for 40K, respectively. All values were much lower than the specific activity limit set by the international legislation at 600 Bq/kg f.m. for 137Cs and at 1,258 Bq/kg f.m. for 40K, respectively. Experimental activity concentrations allowed us to determine the effective dose due to the ingestion of mushrooms by adult members of the population. It was found in the range from 0.25 to 1.35 μSv/y, much lower than the recommended level for the public (1 mSv/y). Data obtained in this article provide useful information on the environmental risk and can be further used for a radiological mapping of the studied area.
{"title":"Radioactivity in wild-growing mushrooms of the Calabria region, south of Italy","authors":"F. Caridi, G. Belmusto","doi":"10.1080/23311940.2017.1354957","DOIUrl":"https://doi.org/10.1080/23311940.2017.1354957","url":null,"abstract":"Abstract Wild-growing mushrooms are a complementary foodstuff, widely consumed as a delicacy, in Italy. They are considered excellent bioindicators of environmental pollution and the accumulation of radionuclides can pose a radiological hazard. 137Cs and 40K activity concentrations were measured through HPGe gamma-spectrometry in different mushroom species (Agaricus arvensis, Leccinum quercinum, Boletus aereus, Lactarius deliciosus, Boletus edulis, Macrolepiota konradii, Cantharellus lutescens) collected from four different sampling sites in the Calabria region, south of Italy. Experimental values were found to be in the range from (0.3 ± 0.1) Bq/kg f.m. (fresh mass) to (73.1 ± 4.6) Bq/kg f.m. for 137Cs and from (46.9 ± 10.7) Bq/kg f.m. to (161.3 ± 12.9) Bq/kg f.m. for 40K, respectively. All values were much lower than the specific activity limit set by the international legislation at 600 Bq/kg f.m. for 137Cs and at 1,258 Bq/kg f.m. for 40K, respectively. Experimental activity concentrations allowed us to determine the effective dose due to the ingestion of mushrooms by adult members of the population. It was found in the range from 0.25 to 1.35 μSv/y, much lower than the recommended level for the public (1 mSv/y). Data obtained in this article provide useful information on the environmental risk and can be further used for a radiological mapping of the studied area.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1354957","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41573250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1312751
A. Hossain, M. Akbar, A. Wazwaz
Abstract The Kundu–Eckhaus equation and the derivative nonlinear Schrodinger equation describe various physical processes in nonlinear optics, plasma physics, fluid mechanics, magneto-hydrodynamic equation in the presence of the Hall Effect. Thus, closed form solutions of these equations are very important to realize the obscurity of the phenomena. The modified simple equation (MSE) method is highly effective and competent mathematical tool to examine closed form wave solutions of nonlinear evolution equations (NLEEs) arising in mathematical physics, applied mathematics and engineering. In this article, the MSE method is suggested and executed to construct closed form wave solutions of the above-mentioned equations involving parameters. When the parameters receive special values, impressive solitary wave solutions are derived from the exact solutions.
{"title":"Closed form solutions of complex wave equations via the modified simple equation method","authors":"A. Hossain, M. Akbar, A. Wazwaz","doi":"10.1080/23311940.2017.1312751","DOIUrl":"https://doi.org/10.1080/23311940.2017.1312751","url":null,"abstract":"Abstract The Kundu–Eckhaus equation and the derivative nonlinear Schrodinger equation describe various physical processes in nonlinear optics, plasma physics, fluid mechanics, magneto-hydrodynamic equation in the presence of the Hall Effect. Thus, closed form solutions of these equations are very important to realize the obscurity of the phenomena. The modified simple equation (MSE) method is highly effective and competent mathematical tool to examine closed form wave solutions of nonlinear evolution equations (NLEEs) arising in mathematical physics, applied mathematics and engineering. In this article, the MSE method is suggested and executed to construct closed form wave solutions of the above-mentioned equations involving parameters. When the parameters receive special values, impressive solitary wave solutions are derived from the exact solutions.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1312751","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46992008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1396948
A. Hossain, M. Akbar, M. Azad
Abstract The exploration of closed form wave solutions of nonlinear evolution equations (NLEEs) is an important research area in the field of physical sciences and engineering. In this article, we investigate closed form wave solution of two nonlinear equations, namely, the time regularized long wave equation and the (2 + 1)-dimensional nonlinear Schrodinger equation by the modified simple equation method. These equations play significant role in nonlinear sciences. The solutions are obtained in explicit form of the variables in the considered equations. The derived solutions are revealed in the form of exponential and trigonometric functions including solitary and periodic solutions. It is shown that the method is effective and an essential mathematical tool for constructing the closed form wave solutions of NLEEs in mathematical physics.
{"title":"Closed form wave solutions of two nonlinear evolution equations","authors":"A. Hossain, M. Akbar, M. Azad","doi":"10.1080/23311940.2017.1396948","DOIUrl":"https://doi.org/10.1080/23311940.2017.1396948","url":null,"abstract":"Abstract The exploration of closed form wave solutions of nonlinear evolution equations (NLEEs) is an important research area in the field of physical sciences and engineering. In this article, we investigate closed form wave solution of two nonlinear equations, namely, the time regularized long wave equation and the (2 + 1)-dimensional nonlinear Schrodinger equation by the modified simple equation method. These equations play significant role in nonlinear sciences. The solutions are obtained in explicit form of the variables in the considered equations. The derived solutions are revealed in the form of exponential and trigonometric functions including solitary and periodic solutions. It is shown that the method is effective and an essential mathematical tool for constructing the closed form wave solutions of NLEEs in mathematical physics.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1396948","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41892171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1391734
Saleem Ayaz Khan, S. Azam, M. Kanoun, G. Murtaza, M. Rani, S. Goumri‐Said
Abstract Cd-doped ZnO nanosheet (ZnO NS) were investigated using a full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) to calculate the electronic structure and its optical response. The calculated band structures have shown that the Cd-doped ZnO NS is a direct band gap semiconductor at Γ with 1.50 eV band gap. The contribution of each atom/orbital were commented in light of total and partial densities of states. We also derived the optical constants (mainly the dielectric constants ε1(0) and ε2(0)), the absorption coefficient I(ω), refractive index n(ω), extinction coefficient k(ω), and energy-loss function L(ω). The spectrum of absorption coefficient has revealed to increase rapidly for photon energies higher than 2.5 eV. The absorption spectrum was found to be limited in energy region due to different contributions electronic transitions that occurred within ZnO NS and effect of Cd doping. Reducing the band gap of ZnO NS to low values is suitable process for light-emitting devices and solar cells applications.
{"title":"Tailoring the electronic structure and optical properties of cadmium-doped zinc oxides nanosheet","authors":"Saleem Ayaz Khan, S. Azam, M. Kanoun, G. Murtaza, M. Rani, S. Goumri‐Said","doi":"10.1080/23311940.2017.1391734","DOIUrl":"https://doi.org/10.1080/23311940.2017.1391734","url":null,"abstract":"Abstract Cd-doped ZnO nanosheet (ZnO NS) were investigated using a full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) to calculate the electronic structure and its optical response. The calculated band structures have shown that the Cd-doped ZnO NS is a direct band gap semiconductor at Γ with 1.50 eV band gap. The contribution of each atom/orbital were commented in light of total and partial densities of states. We also derived the optical constants (mainly the dielectric constants ε1(0) and ε2(0)), the absorption coefficient I(ω), refractive index n(ω), extinction coefficient k(ω), and energy-loss function L(ω). The spectrum of absorption coefficient has revealed to increase rapidly for photon energies higher than 2.5 eV. The absorption spectrum was found to be limited in energy region due to different contributions electronic transitions that occurred within ZnO NS and effect of Cd doping. Reducing the band gap of ZnO NS to low values is suitable process for light-emitting devices and solar cells applications.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1391734","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48275393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1376899
Christopher S. Perreault, N. Velisavljevic, Y. Vohra
Abstract The most incompressible transition metal osmium (Os) has been studied under high pressure. There is significant interest in Os because of the structural anomalies attributed to topological transitions in the Fermi surface for valence electrons in the hexagonal close-packed phase. We report on measurements of structural parameters and equation of state on Os metal to a pressure of 207 GPa at ambient temperature using platinum as a pressure standard. We obtained angle-dispersive X-ray diffraction data at a synchrotron source with closely spaced pressure intervals to observe any discontinuities or anomalies in the axial c/a ratio at high pressures. Rietveld refinements of X-ray diffraction data show a slowly varying axial ratio (c/a) with a broad minimum at 75 GPa. Our data do not provide any evidence of anomalous behavior in the c/a ratio in Os at 25 or 150 GPa as have been reported in previous studies. Our experimental results are in agreement with theoretical calculations that do not predict any anomalous behavior in c/a ratio in Os under extreme conditions. We present an equation of state for Os to 207 GPa (V/V0 = 0.761) at ambient temperature and compare our results with the previously published data.
{"title":"High-pressure structural parameters and equation of state of osmium to 207 GPa","authors":"Christopher S. Perreault, N. Velisavljevic, Y. Vohra","doi":"10.1080/23311940.2017.1376899","DOIUrl":"https://doi.org/10.1080/23311940.2017.1376899","url":null,"abstract":"Abstract The most incompressible transition metal osmium (Os) has been studied under high pressure. There is significant interest in Os because of the structural anomalies attributed to topological transitions in the Fermi surface for valence electrons in the hexagonal close-packed phase. We report on measurements of structural parameters and equation of state on Os metal to a pressure of 207 GPa at ambient temperature using platinum as a pressure standard. We obtained angle-dispersive X-ray diffraction data at a synchrotron source with closely spaced pressure intervals to observe any discontinuities or anomalies in the axial c/a ratio at high pressures. Rietveld refinements of X-ray diffraction data show a slowly varying axial ratio (c/a) with a broad minimum at 75 GPa. Our data do not provide any evidence of anomalous behavior in the c/a ratio in Os at 25 or 150 GPa as have been reported in previous studies. Our experimental results are in agreement with theoretical calculations that do not predict any anomalous behavior in c/a ratio in Os under extreme conditions. We present an equation of state for Os to 207 GPa (V/V0 = 0.761) at ambient temperature and compare our results with the previously published data.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1376899","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44484218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23311940.2017.1327697
V. Degtyareva
Abstract Group I elements—alkali metals Li, Na, K, Rb and Cs—are examples of simple metals with one s electron in the valence band. Under pressure these elements display unusually complex structural behaviour transforming from close-packed to low symmetry open-packed structures. Unexpectedly complex form was found for melting curves of alkalis under compression with an initial increase in the melting temperature in accordance with Lindemann criterion and a further decrease to a very low melting point. To understand complex and low symmetry crystal structures in compressed alkalis, a transformation of the electron energy levels was suggested which involves an overlap between the valence band and outer core electrons. Within the model of the Fermi sphere–Brillouin zone interaction one can understand the complex melting curve of alkalis.
{"title":"Electronic origin of melting T–P curves of alkali metals with negative slope and minimum","authors":"V. Degtyareva","doi":"10.1080/23311940.2017.1327697","DOIUrl":"https://doi.org/10.1080/23311940.2017.1327697","url":null,"abstract":"Abstract Group I elements—alkali metals Li, Na, K, Rb and Cs—are examples of simple metals with one s electron in the valence band. Under pressure these elements display unusually complex structural behaviour transforming from close-packed to low symmetry open-packed structures. Unexpectedly complex form was found for melting curves of alkalis under compression with an initial increase in the melting temperature in accordance with Lindemann criterion and a further decrease to a very low melting point. To understand complex and low symmetry crystal structures in compressed alkalis, a transformation of the electron energy levels was suggested which involves an overlap between the valence band and outer core electrons. Within the model of the Fermi sphere–Brillouin zone interaction one can understand the complex melting curve of alkalis.","PeriodicalId":43050,"journal":{"name":"Cogent Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23311940.2017.1327697","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49471811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：