scholarly journals Wide range equation of state for fluid hydrogen from density functional theory

2013 ◽  
Vol 20 (9) ◽  
pp. 092703 ◽  
Author(s):  
Cong Wang ◽  
Ping Zhang
Keyword(s):  
Density Functional Theory ◽  
Equation Of State ◽  
Density Functional ◽  
Functional Theory ◽  
Wide Range ◽  
Range Equation

scholarly journals Equation of state of argon : experiments on Z, density functional theory (DFT) simulations, and wide-range model.

2012 ◽  
Author(s):  
John H. Carpenter ◽  
Seth Root ◽  
Kyle Robert Cochrane ◽  
Dawn G. Flicker ◽  
Thomas Kjell Rene Mattsson
Keyword(s):  
Density Functional Theory ◽  
Equation Of State ◽  
Density Functional ◽  
Functional Theory ◽  
Wide Range ◽  
Dft Simulations

Sb-terminated InAs(001)-(2×4) and (2×8) studied using scanning tunneling microscopy and ab initio density functional theory

2001 ◽  
Vol 692 ◽  
Author(s):  
William Barvosa-Carter ◽  
Frank Grosse ◽  
James H. G. Owen ◽  
Jennifer J. Zinck
Keyword(s):  
Density Functional Theory ◽  
Scanning Tunneling Microscopy ◽  
Ab Initio ◽  
Density Functional ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Functional Theory ◽  
Subsequent Formation ◽  
Wide Range ◽  
Symmetry Surface

AbstractWe have studied the structure of MBE-grown InAs(001)-(2×4) surfaces exposed to low Sb2 fluxes by scanning tunneling microscopy (STM) and ab initio density functional theory (DFT). Experimentally, we observe an Sb-terminated α2(2×4) phase over a wide range of temperatures (400–510 °C) for low Sb2 flux (<0.1 ML/s), whereas temperature and As2 flux must be carefully controlled to achieve the same As-terminated surface structure. At lower temperatures, we observe indications of an Sb-terminated (2×8) symmetry surface phase, and we report briefly on its proposed structure and stability, as well as its possible role in subsequent formation of the Sb-terminated (1×3) phase found at typical Sb2 fluxes used during heterostructure growth.

Ab Initio Theoretical Studies of Relative Stabilities and IR Spectrum of 5-Methylcytosine Tautomers

2003 ◽  
Vol 2003 (4) ◽  
pp. 195-199 ◽  
Author(s):  
Lida Ghassemzadeh ◽  
Majid Monajjemi ◽  
Karim Zare
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Relative Energy ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Relative Stabilities ◽  
B3lyp Method ◽  
Wide Range ◽  
Good Agreement

The structure and relative energies of the tautomers of 5-methylcytosine in the gasphase and in different solvents are predicted using MP2 and density functional theory methods. The order of stability for these tautomers is C3>C1>C2>C4>C5>C6 calculated by MP2 and C1>C3>C2>C4>C5>C6 calculated by the B3LYP method. Relative energy calculations are performed in wide range of solvent dielectrics and in all solvents the oxo-amino C1 is predicted as the most stable tautomer. The infrared spectra of two dominant tautomers are calculated in the gas phase using HF and density functional theory. Good agreement between calculated (DFT) and experimental harmonic vibrational frequencies is found.

scholarly journals Calculation of the Detonation State of HN3 with Quantum Accuracy

2020 ◽  
Author(s):  
Cong Huy Pham ◽  
Rebecca Lindsey ◽  
Laurence E. Fried ◽  
Nir Goldman
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Potential Energy ◽  
Force Field ◽  
Density Functional ◽  
Energy Surface ◽  
Detonation Properties ◽  
Training Set ◽  
Functional Theory ◽  
Wide Range

<div>HN<sub>3</sub> is a unique liquid energetic material that exhibits ultrafast detonation chemistry and a transition to metallic states during detonation. We combine the ChIMES many-body reactive force field and the extended-Lagrangian multiscale shock technique (MSST) molecular dynamics method to calculate the detonation properties of HN<sub>3</sub> with the accuracy of Kohn-Sham density-functional theory. ChIMES is based on a Chebyshev polynomial expansion and can accurately reproduce density-functional theory molecular dynamics (DFT-MD) simulations for a wide range of unreactive and decomposition conditions of liquid HN<sub>3</sub>. We show that addition of random displacement configurations and the energies of gas-phase equilibrium products in the training set allows ChIMES to efficiently explore the complex potential energy surface. Schemes for selecting force field parameters and the inclusion of stress tensor and energy data in the training set are examined. Structural and dynamical properties, as well as chemistry predictions for the resulting models are benchmarked against DFT-MD. We demonstrate that the inclusion of explicit four-body energy terms is necessary to capture the potential energy surface across a wide range of conditions. The present force field, which was fit to a balance of forces, energies, and stress tensors yields excellent agreement with DFT, while exhibiting an orders-of-magnitude increase in computational efficiency over DFT-MD. Our results generally retain the accuracy of DFT-MD while yielding a high degree of computational efficiency, allowing simulations to approach orders of magnitude larger time and spatial scales. The techniques and recipes for MD model creation we present allow for direct simulation of nanosecond shock compression experiments and calculation of the detonation properties of materials with the accuracy of Kohn-Sham density-functional theory.</div>

scholarly journals Controlling the Lithium Intercalation Voltage in the Li(Mn1-xNix)2O4 Spinel via Tuning of the Ni Concentration: a Density Functional Theory Study

2021 ◽  
Vol 74 ◽  
Author(s):  
Kemeridge T. Malatji ◽  
David Santos-Carballal ◽  
Umberto Terranova ◽  
Phuti E. Ngoepe ◽  
Nora H. de Leeuw
Keyword(s):  
Solid Solution ◽  
Density Functional Theory ◽  
Cathode Material ◽  
Lithium Ion Batteries ◽  
Density Functional ◽  
Lithium Ion ◽  
Lithium Intercalation ◽  
Functional Theory ◽  
Teller Distortion ◽  
Wide Range

ABSTRACT LiMn2O4 spinel is a promising cathode material for secondary lithium-ion batteries. Despite showing a high average voltage of lithium intercalation, the material is structurally unstable, undergoing lowering of the crystal symmetry due to Jahn-Teller distortion of the six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional dopant to improve the structural stability of LiMn2O4 and enhance the average lithium intercalation voltage, the thermodynamics of the Ni incorporation and its effect on the electrochemical properties of this spinel material are not yet known. In this work, we have employed density functional theory calculations with a Hubbard Hamiltonian (DFT+u) to investigate the thermodynamics of cation mixing in the Li(Mn1_xNix)2O4 solid solution. Our results suggest LiMn1.5Ni0.5O4 is the most stable composition from room temperature up to at least 1000 K, in agreement with experiments. We also found that the configurational entropy is much lower than the maximum entropy at 1000 K, indicating that higher temperatures are required to reach a fully disordered solid solution. A maximum average lithium intercalation voltage of 4.8 eV was calculated for the LiMn1.5Ni0.5O4 composition, which is very close to the experimental value. The temperature was found to have a negligible effect on the Li intercalation voltage of the most stable composition. The findings reported here support the application of LiMn1.5Ni0.5O4 as a suitable cathode material for lithium-ion batteries, with a highly stable voltage of intercalation under a wide range of temperatures. Keywords: Spinel, equilibrium concentration, mixing thermodynamics, solid-state chemistry and lithium voltage of intercalation.

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