Ground-State and Thermodynamical Properties of Uranium Mononitride from Anharmonic First-Principles Theory

We report on an advanced density-functional theory (DFT) approach for investigating the ground-state and thermodynamical properties of uranium mononitride (UN). The electronic structure for UN at zero temperature is obtained from DFT that utilizes the generalized gradient approximation (GGA) for the electron exchange and correlation functional and includes spin-orbit interaction and an extension with orbital polarization. Thermodynamical properties are computed within the quasi-harmonic approximation in the Debye–Grüneisen model while anharmonicity is captured in the self-consistent ab initio lattice dynamics (SCAILD) scheme. Anharmonic phonons have heretofore never been modeled from first-principles for UN but they turn out to be important. The computed free energy compares well with that of a CALPHAD (CALculation of PHAse Diagrams) assessment of available experimental data.

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FIRST-PRINCIPLES STUDY OF MAGNETISM AND DEFECT STATE PROPERTIES OF ANTIPEROVSKITE GaC1-xMn3

Modern Physics Letters B ◽

10.1142/s0217984910023001 ◽

2010 ◽

Vol 24 (10) ◽

pp. 953-962 ◽

Cited By ~ 2

Author(s):

L. HUA ◽

L. WANG ◽

L. F. CHEN

Keyword(s):

Ground State ◽

First Principles ◽

Density Functional ◽

Unit Cell Volume ◽

Magnetic Transition ◽

Generalized Gradient ◽

Functional Theory ◽

Generalized Gradient Approximation ◽

Spin Polarized ◽

Volume Decrease

We have investigated the electronic and magnetic properties of GaC 1-x Mn 3 (x = 0, 0.125, 0.25) using first-principles density functional theory within the generalized gradient approximation (GGA) + U schemes. The crystal structures of the compounds are cubic for x = 0, 0.125, 0.25. The lattice parameters and unit cell volume decrease as the C vacancy increase. Our spin polarized calculations give metallic ground state for x = 0, 0.125, 0.25. The magnetic structure for x = 0, 0.125 are antiferromagnetic, while for x = 0.25 it is ferromagnetic. From the density of states (DOS), the hybridization between the C 2p and Mn 3d state is the main reason for magnetic transition.

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Lattice dynamics, phonon vibrational spectra, and thermal properties of tetragonal SrPt3P: a first-principles study

RSC Advances ◽

10.1039/c5ra24600h ◽

2016 ◽

Vol 6 (32) ◽

pp. 27060-27067 ◽

Cited By ~ 2

Author(s):

Xiu-Qing Zhang ◽

Zhao-Yi Zeng ◽

Yan Cheng ◽

Guang-Fu Ji

Keyword(s):

Density Functional Theory ◽

Thermal Properties ◽

Vibrational Spectra ◽

First Principles ◽

Lattice Dynamics ◽

Density Functional ◽

Generalized Gradient ◽

Functional Theory ◽

Generalized Gradient Approximation ◽

First Principles Study

The phonon vibrational spectra and thermal properties of the platinum-based superconductor SrPt3P are investigated by the generalized gradient approximation (GGA) in the framework of density functional theory (DFT).

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Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations

Canadian Journal of Physics ◽

10.1139/p06-008 ◽

2006 ◽

Vol 84 (2) ◽

pp. 115-120 ◽

Cited By ~ 3

Author(s):

G Y Gao ◽

K L Yao ◽

Z L Liu

Keyword(s):

Electronic Structure ◽

First Principles ◽

Density Functional ◽

First Principles Calculations ◽

Generalized Gradient ◽

Functional Theory ◽

Exchange Correlation ◽

Pseudopotential Calculations ◽

Correlation Potential ◽

Density Contour

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b

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Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

Zeitschrift für Naturforschung A ◽

10.1515/zna-2009-5-615 ◽

2009 ◽

Vol 64 (5-6) ◽

pp. 399-404 ◽

Cited By ~ 1

Author(s):

Zi-Jiang Liu ◽

Xiao-Ming Tan ◽

Yuan Guo ◽

Xiao-Ping Zheng ◽

Wen-Zhao Wu

Keyword(s):

Thermodynamic Properties ◽

First Principles ◽

Density Functional ◽

High Pressures ◽

Local Density ◽

Harmonic Approximation ◽

Debye Model ◽

Functional Theory ◽

Casio3 Perovskite ◽

First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

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GGA/PBE study of the spin isomers of Fe34,40, Co23,34, and Co12Cu Clusters with Selected Geometries

Journal of the Mexican Chemical Society ◽

10.29356/jmcs.v56i3.298 ◽

2017 ◽

Vol 56 (3) ◽

Author(s):

Faustino Aguilera-Granja ◽

Andrés Vega ◽

Luis Carlos Balbás

Keyword(s):

Ground State ◽

Density Functional ◽

Energy Difference ◽

Many Body ◽

Generalized Gradient ◽

Structural Isomers ◽

Functional Theory ◽

Ferromagnetic Ground State ◽

Spin Isomers ◽

Pseudo Potential

In a recent beam deflecting experiment was found that high and low spin states of pure Fen and Con clusters with n ≤ 300 atoms coexist at cryogenic temperatures. In this work we have studied the high spin (HS) and low spin (LS) states of several structural isomers of Co23, Co34, Fe34, and Fe40 using the generalized gradient approximation (GGA) to density functional theory as implemented in the first-principles pseudo-potential code SIESTA. The calculated energy difference between these HS and LS isomers is not consistent with the observed coexistence, which can be due to an insufficient account of many body correlation effects in the GGA description, or to unknown isomer structures of these clusters. We have calculated within the same tools the magnetic isomers of Co12Cu cluster aimed to re-visit a former DFT prediction of an anti-ferromagnetic ground state. We find, however, a ferromagnetic ground state as expected on physical grounds. Our results exemplify the difficulties of the current DFT approaches to describe the magnetic properties of transition metal systems.

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First-Principles Study of Interaction of Lithium Atoms with (3, 3) Carbon Nanotubes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.687-691.4311 ◽

2014 ◽

Vol 687-691 ◽

pp. 4311-4314 ◽

Cited By ~ 1

Author(s):

Shun Fu Xu ◽

Ling Min Li

Keyword(s):

Carbon Nanotubes ◽

First Principles ◽

Density Functional ◽

Vacancy Defect ◽

Single Wall Carbon Nanotubes ◽

Generalized Gradient ◽

Hydrogen Atoms ◽

Functional Theory ◽

Vacancy Defects ◽

Adsorption Mechanisms

In this paper, we have employed first-principles calculations to investigate the adsorption mechanisms of one lithium atom on the sidewalls of 1/2/3 H-adsorbed indefective/defective (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. Our calculations are performed within density functional theory (DFT) under the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE).Our results show that the lithium atoms strongly binds to the H-adsorbed (3, 3) nanotube. Lithium atoms can chemically adsorb on (3, 3) nanotube with the vacancy defect (MVD) without any energy barrier. The lithium adsorption will enhance the electrical conductivity of the nanotube. Further more, the structure of the (3, 3) nanotube with the MVD and hydrogen atoms will become more stable after the three kinds of lithium adsorption.

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Many-Body Effects in FeN4 Center Embedded in Graphene

Applied Sciences ◽

10.3390/app10072542 ◽

2020 ◽

Vol 10 (7) ◽

pp. 2542 ◽

Cited By ~ 1

Author(s):

Andrew Allerdt ◽

Hasnain Hafiz ◽

Bernardo Barbiellini ◽

Arun Bansil ◽

Adrian E. Feiguin

Keyword(s):

Transition Metal Complexes ◽

First Principles ◽

Density Functional ◽

Coulomb Repulsion ◽

Density Matrix Renormalization Group ◽

Orbital Interaction ◽

Many Body ◽

Generalized Gradient ◽

Functional Theory ◽

Density Matrix Renormalization

We introduce a computational approach to study porphyrin-like transition metal complexes, bridging density functional theory and exact many-body techniques, such as the density matrix renormalization group (DMRG). We first derive a multi-orbital Anderson impurity Hamiltonian starting from first principles considerations that qualitatively reproduce generalized gradient approximation (GGA)+U results when ignoring inter-orbital Coulomb repulsion U ′ and Hund exchange J. An exact canonical transformation is used to reduce the dimensionality of the problem and make it amenable to DMRG calculations, including all many-body terms (both intra- and inter-orbital), which are treated in a numerically exact way. We apply this technique to FeN 4 centers in graphene and show that the inclusion of these terms has dramatic effects: as the iron orbitals become single occupied due to the Coulomb repulsion, the inter-orbital interaction further reduces the occupation, yielding a non-monotonic behavior of the magnetic moment as a function of the interactions, with maximum polarization only in a small window at intermediate values of the parameters. Furthermore, U ′ changes the relative position of the peaks in the density of states, particularly on the iron d z 2 orbital, which is expected to affect the binding of ligands greatly.

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Thermodynamics of Uranium Tri-Iodide from Density-Functional Theory

Applied Sciences ◽

10.3390/app10113914 ◽

2020 ◽

Vol 10 (11) ◽

pp. 3914

Author(s):

Per Söderlind ◽

Aurélien Perron ◽

Emily E. Moore ◽

Alexander Landa ◽

Tae Wook Heo

Keyword(s):

Experimental Data ◽

Density Functional Theory ◽

Heat Capacity ◽

Density Functional ◽

Thermodynamic Assessment ◽

Harmonic Approximation ◽

Metallic System ◽

Generalized Gradient ◽

Functional Theory ◽

Generalized Gradient Approximation

Density-functional theory (DFT) is employed to investigate the thermodynamic and ground-state properties of bulk uranium tri-iodide, UI3. The theory is fully relativistic and electron correlations, beyond the DFT and generalized gradient approximation, are addressed with orbital polarization. The electronic structure indicates anti-ferromagnetism, in agreement with neutron diffraction, with band gaps and a non-metallic system. Furthermore, the formation energy, atomic volume, crystal structure, and heat capacity are calculated in reasonable agreement with experiments, whereas for the elastic constants experimental data are unavailable for comparison. The thermodynamical properties are modeled within a quasi-harmonic approximation and the heat capacity and Gibbs free energy as functions of temperature agree with available calculation of phase diagram (CALPHAD) thermodynamic assessment of the experimental data.

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THERMODYNAMIC PROPERTIES OF MgSiO3 POST-PEROVSKITE

Modern Physics Letters B ◽

10.1142/s0217984910022391 ◽

2010 ◽

Vol 24 (03) ◽

pp. 315-324

Author(s):

ZI-JIANG LIU ◽

XIAO-WEI SUN ◽

CAI-RONG ZHANG ◽

LI-NA TIAN ◽

YUAN GUO

Keyword(s):

Thermodynamic Properties ◽

First Principles ◽

Density Functional ◽

High Pressures ◽

Local Density ◽

Harmonic Approximation ◽

Debye Model ◽

Functional Theory ◽

High Pressures And Temperatures ◽

First Time

The thermodynamic properties of MgSiO 3 post-perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines with ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state of MgSiO 3 post-perovskite is in excellent agreement with the latest observed values. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion, and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

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THEORETICAL INVESTIGATION OF THE ELASTIC PROPERTIES AND LATTICE DYNAMICS OF THE MgSxSe1-x ALLOY

Modern Physics Letters B ◽

10.1142/s0217984907012621 ◽

2007 ◽

Vol 21 (05) ◽

pp. 249-259 ◽

Cited By ~ 9

Author(s):

K. BOUAMAMA ◽

P. DJEMIA

Keyword(s):

Elastic Properties ◽

First Principles ◽

Lattice Dynamics ◽

Density Functional ◽

Local Density ◽

Lattice Parameter ◽

First Principles Calculations ◽

Virtual Crystal Approximation ◽

Functional Theory ◽

Density Functional Perturbation Theory

Structural and elastic properties as well as lattice dynamics of ternary MgS x Se 1-x alloy have been studied using first-principles calculations. These are done using density functional theory (DFT) and density functional perturbation theory (DFPT) within the local density approximation (LDA) and employing the virtual-crystal approximation (VCA). We found that the lattice parameter, the elastic constants and the phonon frequencies follow a quadratic law in x.

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