MCML : Combining physical constraints with experimental data for a multi‐purpose meta‐generalized gradient approximation

2021 ◽  
Author(s):  
Kristopher Brown ◽  
Yasheng Maimaiti ◽  
Kai Trepte ◽  
Thomas Bligaard ◽  
Johannes Voss
Keyword(s):  
Experimental Data ◽  
Generalized Gradient ◽  
Physical Constraints ◽  
Generalized Gradient Approximation

The physical properties of ThCr2Si2-type superconductors MPd2P2 (M = Y, La): A theoretical investigation

2018 ◽  
Vol 32 (28) ◽  
pp. 1850312
Author(s):  
Md. Lokman Ali ◽  
Md. Tosaddek Hossen ◽  
Shahin Alam ◽  
Md. Sadek Hossain ◽  
Jakiul Islam ◽  
...  
Keyword(s):  
Experimental Data ◽  
Elastic Constants ◽  
Structural Data ◽  
Computer Code ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Anisotropic Factor ◽  
Optical Functions ◽  
Debye Temperatures ◽  
Ductile Behavior

The structural stability, elastic, mechanical, optical characteristics and Debye temperature of single crystalline superconductors MPd2P2 (M = Y, La) were investigated by using the ab initio technique. We have carried out the plane wave pseudopotential within the generalized gradient approximation (GGA) implemented in the CASTEP computer code. Our investigated results of structural data are in well consistent with the previous experimental data. The bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio v, hardness H, and anisotropic factor A of MPd2P2 (M = Y, La) compounds were evaluated from the calculated elastic constants. The analysis of ratio B/G shows that the MPd2P2 superconductors are in ductile behavior. The Debye temperatures are also investigated from the elastic constants. Finally, the optical functions including reflectivity, absorption coefficient, loss function, conductivity, refractive index, dielectric function are calculated and analyzed.

scholarly journals Thermodynamics of Uranium Tri-Iodide from Density-Functional Theory

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.

MODELLING OF NEUTRAL VACANCIES IN FORSTERITE MINERAL

2013 ◽  
Vol 27 (25) ◽  
pp. 1350141 ◽  
Author(s):  
ARVIDS STASHANS ◽  
YETZABEL FLORES
Keyword(s):  
Experimental Data ◽  
Chemical Bonding ◽  
Density Functional ◽  
Local Energy ◽  
Generalized Gradient ◽  
Covalent Character ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Interaction Law ◽  
Equilibrium Geometries

Density functional theory and generalized gradient approximation have been employed to study Mg , Si and O vacancies in the Mg 2 SiO 4 forsterite mineral. Microstructure of defect equilibrium geometries, electronic properties as well as chemical bonding in the region surrounding each one of the vacancies have been computed and discussed in detail. It is found that vacancies tend to increase covalent character of the chemical bonding for atoms situated in their vicinity independently of the type of vacancy. Nevertheless, obtained atomic distortion in the region surrounding vacancies generally obeys Coulomb electrostatic interaction law. Local energy states are found in the band-gap region due to the occurrence of vacancy-type defects. These findings are discussed in light of the available experimental data.

Structural Stability and Chemical Bonding of TiN: Ab Initio Study

2014 ◽  
Vol 1047 ◽  
pp. 41-44
Author(s):  
Mamta Chauhan ◽  
Dinesh Chandra Gupta ◽  
Idris Hamid Bhat
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
High Pressure ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
B2 Phase ◽  
Pseudo Potential ◽  
Electronic Behavior

We have performed ab-initio calculations to investigate the structural and electronic behavior of TiN in the stable B1 and high pressure B2 phases using pseudo-potential plane wave approach within the framework of density functional theory. The calculated results show agreement with the experimental data. The present electronic behavior, determined by total energy calculations with generalized gradient approximation for exchange and correlation interactions, is observed to be similar in both B1 and B2 phases showing metallic, covalent as well as ionic bonding of TiN. The investigations in B2 phase need validation experimentally as well as theoretically.

scholarly journals Theoretical calculation for the phonon spectrum and thermodynamic functions of vanadium and its hydride

2021 ◽  
Vol 252 ◽  
pp. 03039
Author(s):  
Qiang Wei-rong ◽  
Wang Xiao-mei ◽  
Liu Wei-qi
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Free Energies ◽  
Generalized Gradient ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Density Functional Perturbation Theory ◽  
Densities Of States

Based on density functional theory(DFT), using virtual crystal approximation and generalized gradient approximation(GGA)with pseudopotential method, the lattices and energies for five crystallines of vanadium hydrides are optimized and calculated. The phonon densities of states are calculated based on density functional perturbation theory(DFPT). The standard Heat capacities, Entropies, Helmholtz free energies and Gibbs functions of vanadium and its hydride are deduced at 298.15K. The calculated results are discussed and compared with experimental data.

Optical and Transport Effects in LaGa1-xMnxO3: Experiment and Modeling

2004 ◽  
Vol 834 ◽  
Author(s):  
N. Noginova ◽  
F. Chen ◽  
G. Chelule ◽  
V. I. Gavrilenko
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Energy Structure ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Optical Functions ◽  
Transport Effects ◽  
Electron Energy Structure ◽  
Theoretical Results

AbstractCharge transport and optical properties have been studied experimentally and theoretically in a series of LaGa1-xMnxO3 crystals in the dependence on the material composition. Electron energy structure and optical functions of LaGa1-xMnxO3 are calculated by ab initio pseudopotential method within density functional theory using generalized gradient approximation. Theoretical results are discussed in comparison with the experimental data for different alloy compositions.

First-principles investigation of the elastic and thermodynamic properties of ReC2 (Re = Ho, Nd, Pr)

2015 ◽  
Vol 29 (01) ◽  
pp. 1450256 ◽  
Author(s):  
Wen Huang ◽  
Haichuan Chen
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Lattice Constants ◽  
Generalized Gradient Approximation ◽  
Temperature Melting

The elastic and thermodynamic properties of Re C 2 (Re = Ho , Nd , Pr ) have been investigated by using the first-principles density functional theory within the generalized gradient approximation. The computed lattice constants of Re C 2 are in agreement with the experimental data. The calculated elastic constants reveal that all compounds are mechanically stable. The shear modulus, Young's modulus, Poisson's ratio σ, the ratio B/G, shear anisotropy and elastic anisotropy are also calculated. Finally, the Vicker hardness, Debye temperature, melting point and thermal conductivity have been predicted.

scholarly journals First Principles Study of Cerium Monochalcogenides

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Recep Eryiğit
Keyword(s):  
Experimental Data ◽  
Plane Wave ◽  
Theoretical Investigation ◽  
First Principles ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
First Principles Study ◽  
Dynamical Properties ◽  
Good Agreement

A theoretical investigation of structural, magnetic, electronic, and lattice dynamical properties of cerium monochalcogenides using the generalized gradient approximation (GGA) +Uwithin ultrasoft pseudopotentials and a plane-wave basis is presented. All the calculated quantities, except the local magnetic moments, are found to be in good agreement with the experimental data. The lattice dynamical results indicate a strong chalcogenide dependence for the anomalous features of the phonon dispersions.

First-Principles Investigation of ThO2

2012 ◽  
Vol 535-537 ◽  
pp. 2531-2534 ◽  
Author(s):  
Ya Ping Li ◽  
Ping Qian ◽  
Li Jun Bai ◽  
Jin Chun Li ◽  
Jiang Shen
Keyword(s):  
Experimental Data ◽  
First Principles ◽  
Energy Band ◽  
Local Density Approximation ◽  
Local Density ◽  
Lattice Parameter ◽  
Density Approximation ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Densities Of States

We systematically performed first-principles investigations of the structural properties, electron energy band, and densities of states (DOS) for ThO2. All calculations were carried out using the local density approximation (LDA), generalized gradient approximation (GGA), LDA+U, and GGA+U approaches. We also compared our findings with experimental data and other calculations. The lattice parameter obtained using the GGA+U agrees well with the experimental value.

Interstitial vs. Substitutional Metal Insertion in V2O5 as Post-Lithium Ion Battery Cathode: A Comparative GGA/GGA+U Study with Localized Bases

2020 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Electronic Structure ◽  
Plane Wave ◽  
Transition Metal Oxides ◽  
Reasonable Agreement ◽  
Correction Term ◽  
Lithium Ion ◽  
Generalized Gradient ◽  
Main Group Metals ◽  
Generalized Gradient Approximation ◽  
Metal Insertion

<p></p><p>The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter <i>U</i>. We tune <i>U</i> to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. We find the value for <i>U</i> to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being in reasonable agreement with experiments. We use this computational setup to calculate interstitial and substitutional <a>insertion energies of main group metals in vanadium pentoxide</a> and find <a>interstitial doping to be thermodynamically favored</a>.</p><p></p>

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