The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
P R Levashov - One of the best experts on this subject based on the ideXlab platform.
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ab Initio Calculation of thermodynamic transport and optical properties of ch2 plastics
Physics of Plasmas, 2015Co-Authors: D V Knyazev, P R LevashovAbstract:This work covers an ab Initio Calculation of thermodynamic, transport, and optical properties of plastics of the effective composition CH2 at density 0.954 g/cm3 in the temperature range from 5 kK up to 100 kK. The Calculation is based on the quantum molecular dynamics, density functional theory, and the Kubo-Greenwood formula. The temperature dependence of the static electrical conductivity σ1DC(T) has a step-like shape: σ1DC(T) grows rapidly for 5 kK ≤ T ≤ 10 kK and is almost constant for 20 kK ≤ T ≤ 60 kK. The additional analysis based on the investigation of the electron density of states (DOS) is performed. The rapid growth of σ1DC(T) at 5 kK ≤ T ≤ 10 kK is connected with the increase of DOS at the electron energy equal to the chemical potential ϵ = μ. The frequency dependence of the dynamic electrical conductivity σ1(ω) at 5 kK has the distinct non-Drude shape with the peak at ω ≈ 10 eV. This behavior of σ1(ω) was explained by the dip at the electron DOS.
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transport and optical properties of warm dense aluminum in the two temperature regime ab Initio Calculation and semiempirical approximation
Physics of Plasmas, 2014Co-Authors: D V Knyazev, P R LevashovAbstract:This work is devoted to the investigation of transport and optical properties of liquid aluminum in the two-temperature case. At first optical properties, static electrical, and thermal conductivities were obtained in the ab Initio Calculation which is based on the quantum molecular dynamics, density functional theory, and the Kubo-Greenwood formula. Then the semiempirical approximation was constructed based on the results of our simulation. This approximation yields the dependences σ1DC∝1/Ti0.25 and K∝Te/Ti0.25 for the static electrical conductivity and thermal conductivity, respectively, for liquid aluminum at ρ = 2.70 g/cm3, 3 kK ≤ Ti ≤ Te ≤ 20 kK. Our results are well described by the Drude model with the effective relaxation time τ∝Ti−0.25. We have considered a number of other models for the static electrical and thermal conductivities of aluminum, they are all reduced in the low-temperature limit to the Drude model with different expressions for the relaxation time τ. Our results are not consistent ...
D V Knyazev - One of the best experts on this subject based on the ideXlab platform.
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ab Initio Calculation of thermodynamic transport and optical properties of ch2 plastics
Physics of Plasmas, 2015Co-Authors: D V Knyazev, P R LevashovAbstract:This work covers an ab Initio Calculation of thermodynamic, transport, and optical properties of plastics of the effective composition CH2 at density 0.954 g/cm3 in the temperature range from 5 kK up to 100 kK. The Calculation is based on the quantum molecular dynamics, density functional theory, and the Kubo-Greenwood formula. The temperature dependence of the static electrical conductivity σ1DC(T) has a step-like shape: σ1DC(T) grows rapidly for 5 kK ≤ T ≤ 10 kK and is almost constant for 20 kK ≤ T ≤ 60 kK. The additional analysis based on the investigation of the electron density of states (DOS) is performed. The rapid growth of σ1DC(T) at 5 kK ≤ T ≤ 10 kK is connected with the increase of DOS at the electron energy equal to the chemical potential ϵ = μ. The frequency dependence of the dynamic electrical conductivity σ1(ω) at 5 kK has the distinct non-Drude shape with the peak at ω ≈ 10 eV. This behavior of σ1(ω) was explained by the dip at the electron DOS.
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transport and optical properties of warm dense aluminum in the two temperature regime ab Initio Calculation and semiempirical approximation
Physics of Plasmas, 2014Co-Authors: D V Knyazev, P R LevashovAbstract:This work is devoted to the investigation of transport and optical properties of liquid aluminum in the two-temperature case. At first optical properties, static electrical, and thermal conductivities were obtained in the ab Initio Calculation which is based on the quantum molecular dynamics, density functional theory, and the Kubo-Greenwood formula. Then the semiempirical approximation was constructed based on the results of our simulation. This approximation yields the dependences σ1DC∝1/Ti0.25 and K∝Te/Ti0.25 for the static electrical conductivity and thermal conductivity, respectively, for liquid aluminum at ρ = 2.70 g/cm3, 3 kK ≤ Ti ≤ Te ≤ 20 kK. Our results are well described by the Drude model with the effective relaxation time τ∝Ti−0.25. We have considered a number of other models for the static electrical and thermal conductivities of aluminum, they are all reduced in the low-temperature limit to the Drude model with different expressions for the relaxation time τ. Our results are not consistent ...
Qing Liu - One of the best experts on this subject based on the ideXlab platform.
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FT-IR spectroscopy combined with DFT Calculation to explore solvent effects of vinyl acetate.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2014Co-Authors: Yi Chen, Hui Zhang, Qing LiuAbstract:The infrared vibration frequencies of vinyl acetate (VAc) in 18 different solvents were theoretically computed at Density Function Theory (DFT) B3LYP/6-311G(*) level based on Polarizable Continuum Model (PCM) and experimentally recorded by FT-IR spectroscopy. The solvent-induced long-range bulk electrostatic solvation free energies of VAc (ΔGelec) were calculated by the SMD model. The C=O stretching vibration frequencies of VAc were utilized as a measure of the chemical reactivities of the CC group in VAc. The calculated and experimental C=O stretching vibration frequencies of VAc (νcal(C=O) and νexp(C=O)) were correlated with empirical solvent parameters including the KBM equation, the Swain equation and the linear solvation energy relationships (LSER). Through ab Initio Calculation, assignments of the two C=O absorption bands of VAc in alcohol solvents were achieved. The PCM, SMD and ab Initio Calculation offered supporting evidence to explain the FT-IR experimental observations from differing aspects.
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FT-IR spectroscopy and DFT Calculation study on the solvent effects of benzaldehyde in organic solvents.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2012Co-Authors: Yi Li, Hui Zhang, Qing LiuAbstract:FT-IR spectra of benzaldehyde in 11 different organic solvents were recorded and analyzed. The density functional theory (DFT) B3LYP/6-31G* method was chosen to calculate the infrared spectrum of benzaldehyde in gaseous state. The electrostatic effects of different solvents in benzaldehyde solutions were calculated using DFT with the self-consistent isodensity polarizable continuum model (SCI-PCM). Two remarkable carbonyl (C=O) peaks of benzaldehyde were observed by FT-IR in alcohol solvents, which were caused by different hydrogen bond species and explained by ab Initio Calculation. The results showed that the combination of SCI-PCM model and ab Initio Calculation could give excellent agreements with FT-IR spectra of title compound in solutions.
Jeff Dahn - One of the best experts on this subject based on the ideXlab platform.
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Ab Initio Calculation of the lithium-tin voltage profile
Physical Review B, 1998Co-Authors: I. Courtney, J. Tse, Ou Mao, Jürgen Hafner, Jeff DahnAbstract:An ab Initio pseudopotential plane-wave method was used to calculate the total energies for several structures (Sn, Li2Sn5,Li2Sn5, LiSn, Li7Sn3,Li7Sn3, Li5Sn2,Li5Sn2, Li13Sn5,Li13Sn5, Li7Sn2,Li7Sn2, and Li) of the lithium-tin phase diagram. This information was used to determine a theoretical electrochemical voltage profile, which compares well with experiment for x2.5,x>2.5, it was found that the equilibrium structures predicted by the phase diagram were not formed in the room-temperature electrochemical cell, which explains why the calculated results are less good there. Calculations of this type are useful for materials research in lithium-ion batteries.
Giovanni Onida - One of the best experts on this subject based on the ideXlab platform.
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Ab Initio Calculation of excitonic effects in realistic materials
Comput. Mater. Sci., 1998Co-Authors: Sven Albrecht, Lucia Reining, Giovanni Onida, Rodolfo Del SoleAbstract:Ab Initio Calculations, based on the density functional theory (DFT)\nin the local density approximation (LDA), allow for the description\nof the ground state properties of a wide class of materials. Also\none-quasiparticle excitations can be obtained with good precision\nby adding self-energy corrections to the DFT-LDA eigenvalues. A realistic\ndescription of two-particle excitations, like the creation of electron-hole\npairs in absorption experiments, is hardly feasible for systems where\nthe electron and the hole interact. In this work we show how such\nexcitonic effects can be included in ab Initio electronic structure\nCalculations, via the solution of an effective two-particle equation.\nResults for different systems are presented.
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Ab-Initio Calculation of the Optical Properties of Surfaces
phys. stat. sol. (a), 1998Co-Authors: Giovanni Onida, R Del~Sole, Olivia Pulci, Maurizia Palummo, Lucia ReiningAbstract:The recent development of computational methods using very large plane-wave basis sets, together with the large increase in computer performance, have now made it possible to compute the optical properties of real surfaces within a parameter-free approach. In this work, we describe a scheme for such a Calculation, based on the state-of-the-art techniques for the computation of the ground and excited electronic states. We outline the advantages and the drawbacks related to the introduction of various approximation schemes, as well as the role of the most important convergence parameters. We present examples and applications to GaAs(110) and Si(100) surfaces, comparing the results with those of previous Calculations, both semi-empirical and ab-Initio, and with experimental data.
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Ab Initio Calculation of the quasiparticle spectrum and excitonic effects inO
Physical Review B - Condensed Matter and Materials Physics, 1997Co-Authors: Stefan Albrecht, Giovanni OnidaAbstract:We report an ab Initio Calculation of the binding energies and the nature of the excitonic states in the near-gap absorption spectrum of a real solid, Li2O. We calculate the ground-state properties using density- functional theory together with soft pseudopotentials. Applying Hedin’s GW approximation for the self-energy corrections to the band structure, we determine the minimal gap about 1 eV above the measured absorption onset. Finally, we obtain agreement with experiment by solving an effective two-particle Schrodinger equation for the electron-hole pairs.