scholarly journals Computational Study of A15 Ru-Based Alloys for High-Temperature Structural Applications

2021 ◽  
Author(s):  
Bhila Oliver Mnisi ◽  
Evans Moseti Benecha ◽  
Meriam Malebo Tibane
Keyword(s):  
High Temperature ◽  
Elastic Constants ◽  
Density Functional ◽  
Computational Study ◽  
Dft Methods ◽  
Electronic Density ◽  
Experimental Realization ◽  
Anisotropic Factor ◽  
Structural Applications ◽  
High Magnetic Moment

The structural, magnetic, electronic and elastic properties of A15 X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) binary alloys are investigated using first-principles density functional theory (DFT) methods. Ru-based alloys have attracted remarkable research interest due to their unique properties, which make them suitable for high-temperature structural applications. In this chapter, the properties of several A15 Ru-based alloys are investigated in order to select the best suitable alloy/s for aerospace application. Heats of formation are calculated to determine the thermodynamic stability of the materials. Knowledge of the values of elastic constants is essential for understanding the mechanical properties of the materials. From our calculated elastic constants, the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, melting temperature, anisotropic factor and the ratio B/G are determined. The electronic density of states are calculated and discussed. Lastly, the magnetic properties of A15 X3Ru alloys are studied. Thermodynamically stable Mn3Ru possesses high-magnetic moment compared to other X3Ru alloys, these results could pave way to experimental realization (synthesis) of Mn3Ru material.

scholarly journals Pressure Effect on Elastic Constants and Related Properties of Ti3Al Intermetallic Compound: A First-Principles Study

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2015 ◽  
Author(s):  
Xianshi Zeng ◽  
Rufang Peng ◽  
Yanlin Yu ◽  
Zuofu Hu ◽  
Yufeng Wen ◽  
...  
Keyword(s):  
Intermetallic Compound ◽  
Debye Temperature ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Theoretical Data ◽  
Young’S Moduli ◽  
Anisotropic Factor ◽  
Isotropic Pressure

Using first-principles calculations based on density functional theory, the elastic constants and some of the related physical quantities, such as the bulk, shear, and Young’s moduli, Poisson’s ratio, anisotropic factor, acoustic velocity, minimum thermal conductivity, and Debye temperature, are reported in this paper for the hexagonal intermetallic compound Ti 3 Al. The obtained results are well consistent with the available experimental and theoretical data. The effect of pressure on all studied parameters was investigated. By the mechanical stability criteria under isotropic pressure, it is predicted that the compound is mechanically unstable at pressures above 71.4 GPa. Its ductility, anisotropy, and Debye temperature are enhanced with pressure.

scholarly journals Synthesis, X-Ray Crystallography, Thermal Analysis, and DFT Studies of Ni(II) Complex with 1-Vinylimidazole Ligand

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Fatih Şen ◽  
Ramazan Şahin ◽  
Muharrem Dinçer ◽  
Ömer Andaç ◽  
Murat Taş
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Basis Sets ◽  
Mulliken Charge ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Dft Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Density Functional Theory

The paper presents a combined experimental and computational study of hexa(1-vinylimidazole)Ni(II) perchlorate complex. The complex was prepared in the laboratory and crystallized in the monoclinic space group P21/n with a=8.442(5), b=13.686(8), c=16.041(9) Å, α=γ=90, β=96.638(5), and Z=1. The complex has been characterized structurally (by single-crystal X-Ray diffraction) and its molecular structure in the ground state has been calculated using the density functional theory (DFT) methods with 6-31G(d) and LanL2DZ basis sets. Thermal behaviour and stability of the complex were studied by TGA/DTA analyses. Besides, the nonlinear optical effects (NLO), molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), and the Mulliken charge distribution were investigated theoretically.

First-principles study of the structure, elastic constants, electronic and thermodynamic properties of C15 laves phase ZrMo2

2020 ◽  
Vol 34 (18) ◽  
pp. 2050170
Author(s):  
Xianbo Liu ◽  
Jun Zhu
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constants ◽  
Density Functional ◽  
Debye Model ◽  
State Density ◽  
Electronic Density ◽  
Plane Wave Method ◽  
Electron State Density ◽  
Phonon Spectra ◽  
Theoretical Simulations

The structure, elastic constants and electron state density of ZrMo2 in [Formula: see text]15 phase are investigated by pseudopotential plane-wave method based on density functional theory (DFT). The thermodynamic properties are studied with the quasi-harmonic Debye model. The calculated results are in good agreement with the previous experimental results and theoretical simulations. The calculated phonon spectra and elastic constants show that [Formula: see text]15 phase of ZrMo2 is mechanically stable. Through the analysis of [Formula: see text]/[Formula: see text] value and Poisson’s ratio, [Formula: see text]15 phase of ZrMo2 shows ductility at 0–150 GPa, and it increases with the increment of pressure. We further explore the mechanism of the metallic properties by analyzing the electronic density of states. In addition, Debye temperature, thermal expansion coefficient and heat capacity as a function of pressure and temperature is discussed, respectively.

scholarly journals Computer aided chemical design: using quantum chemical calculations to predict properties of a series of halochromic guaiazulene derivatives

2016 ◽  
Vol 3 (11) ◽  
pp. 160373 ◽  
Author(s):  
Adam W. Woodward ◽  
Ebrahim H. Ghazvini Zadeh ◽  
Mykhailo V. Bondar ◽  
Kevin D. Belfield
Keyword(s):  
Data Storage ◽  
Density Functional ◽  
Computational Study ◽  
Photophysical Properties ◽  
Photon Absorption ◽  
Optoelectronic System ◽  
Dft Methods ◽  
Two Photon Absorption ◽  
Td Dft ◽  
Calculation Results

With the scientific community becoming increasingly aware of the need for greener products and methodologies, the optimization of synthetic design is of greater importance. Building on experimental data collected from a synthesized guaiazulene derivative, a series of analogous structures were investigated with time-dependent density functional theory (TD-DFT) methods in an effort to identify a compound with desirable photophysical properties. This in silico analysis may eliminate the need to synthesize numerous materials that, when investigated, do not possess viable characteristics. The synthesis of several computationally investigated structures revealed discrepancies in the calculation results. Further refined computational study of the molecules yielded results closer to those observed experimentally and helps set the stage for computationally guided design of organic photonic materials. Three novel derivatives were synthesized from guaiazulene, a naturally occurring chromophore, exhibiting distinct halochromic behaviour, which may have potential in a switchable optoelectronic system or combined with a photoacid generator for data storage. The protonated forms were readily excitable via two-photon absorption.

Stability, Mechanical Properties and Electronic Properties of X3Si (X=V, Nb, Cr, Mo and W) from First Principles Calculations

2018 ◽  
Vol 913 ◽  
pp. 596-606
Author(s):  
He Wei ◽  
Yin Li Chen ◽  
Lan Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Transition Metal ◽  
Electronic Properties ◽  
Density Functional ◽  
Metal Silicide ◽  
Electronic Density ◽  
Temperature Oxidation ◽  
Transition Metal Silicide ◽  
Metastable Structure

The transition metal silicide X3Si (X = V, Nb, Cr, Mo and W) was characterized by its low density, high melting point, high temperature hardness, high temperature resistance to wear, high temperature oxidation resistance and corrosion resistance in this paper. For the fields such as aerospace, gas turbine etc, with the application of a new generation of high temperature structural materials, transition metal silicide will be one of their candidate materials. The stability, crystal structure, mechanical properties, electronic properties, Debye temperature and hardness of X3Si(X=V, Nb, Cr, Mo and W) compounds were calculated employing electronic density functional theory (DFT) and the generalized gradient approximation (GGA). The results show that the remaining silicides have stable structures except that W3Si is a metastable structure in X3Si compounds. Based on the stress-strain theory, the bulk modulus, shear modulus, Young's modulus and Poisson's ratio of Cr3Si and Mo3Si were estimated by Voigt-Reuss-Hill method: 248.7 GPa, 158.9 GPa, 393.0 GPa, 0.24 and 249.2 GPa, 134.6 GPa, 342.1 GPa, 0.27. According to the state density (DOS) analysis, we can see that the valence band of X3Si compound is a combination of covalent bond and metal bond. The temperature of Debye of Cr3Si (645.1 K) in X3Si compound is the highest. The hardness of these silicon compounds is evaluated using a semi empirical hardness theory and the result shows that Cr3Si (10.96 GPa) is the hardest compound among them.

First-Principles Calculation of Elastic Constants for FeP

2013 ◽  
Vol 321-324 ◽  
pp. 1761-1765 ◽  
Author(s):  
Jian Ying Li ◽  
Jing Zhang ◽  
Qi Zhi Cao ◽  
Yi Fang Ouyang
Keyword(s):  
Elastic Constants ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Density Functional Theory Method ◽  
First Principles Calculation ◽  
Electronic Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Theoretical Results ◽  
Good Agreement

The elastic constants of FeP with orthorhombic structure were calculated by using the density-functional theory method. The formation enthalpy, electronic density of states, bulk modulus, and lattice parameters of orthorhombic FeP were also calculated. All of the results are in good agreement with the experimental data and theoretical results available. The results indicate that orthorhombic FeP intermetallic compound is brittleness.

scholarly journals Density Functional Theory of Material Design: Fundamentals and Applications - I

2021 ◽  
Author(s):  
Prashant Singh ◽  
Manoj K Harbola
Keyword(s):  
Density Functional Theory ◽  
Schrödinger Equation ◽  
Local Density Approximation ◽  
Schrodinger Equation ◽  
Density Functional ◽  
Local Density ◽  
Density Approximation ◽  
Dft Methods ◽  
Electronic Density ◽  
Functional Theory

Abstract This article is part-I of a review of density-functional theory (DFT) that is the most widely used method for calculating electronic structure of materials. The accuracy and ease of numerical implementation of DFT methods has resulted in its extensive use for materials design and discovery and has thus ushered in the new field of computational material science. In this article we start with an introduction to Schrödinger equation and methods of its solutions. After presenting exact results for some well-known systems, difficulties encountered in solving the equation for interacting electrons are described. How these difficulties are handled using the variational principle for the energy to obtain approximate solutions of the Schrödinger equation is discussed. The resulting Hartree and Hartree-Fock theories are presented along with results they give for atomic and solid-state systems. We then describe Thomas-Fermi theory and its extensions which were the initial attempts to formulate many-electron problem in terms of electronic density of a system. Having described these theories, we introduce modern density functional theory by discussing Hohenberg-Kohn theorems that form its foundations. We then go on to discuss Kohn-Sham formulation of density-functional theory in its exact form. Next, local density approximation is introduced and solutions of Kohn-Sham equation for some representative systems, obtained using the local density approximation, are presented. We end part-I of the review describing the contents of part-II.

scholarly journals Semiconductor Materials for Fabrication of Multi-Color Organic Light-Emitting Diodes (OLEDs)

2021 ◽  
Vol 40 (4) ◽  
pp. 874-882
Author(s):  
Aftab Ahmad ◽  
Nasif Raza Jaffri ◽  
Usama Abrar
Keyword(s):  
Liquid Crystals ◽  
Electronic Properties ◽  
Density Functional ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Dft Methods ◽  
Electronic Density ◽  
Light Emitting ◽  
Organic Light ◽  
Mechanical Methods

This study aims to propose organic materials for the development of light-emitting semiconductor diodes for colored displays. Studies show that these materials are capable of creating a variety of different colors rather than white light. But of Organic Light-Emitting Diodes (OLEDs) are only used as a source of white back-light for OLED displays and liquid crystals are used for color generation. This work suggests that OLEDs can be used to make color displays on their own without the help of Liquid Crystals (LCs). Recently, organic devices are widely under discussion as are comparatively cheap, can be processed economically and effortlessly at ambient temperature besides their effortless handling. The calculation of the electronic properties of molecular species was achieved by the use of ab-initio quantum mechanical methods, i.e., Density Functional Theory (DFT). DFT methods are suited to calculate the electronics properties of the organic molecules, enabling the determination of band gaps and quantum efficiencies. DFT views electron stochastic nature and thus calculates the material’s solid-state properties. DFT calculations on isolated molecules were carried by the Gaussian software package to predict electronic properties. Pentacene is used as test molecule in this work. B3LYP functional use Kohn-Sham orbitals to predict the band energy values said material rather than LDA functional that depends on the value of electronic density at each point on the space. The substitution process was used to make changes in bandgaps; which affect shades of light emitted by OLEDs.

scholarly journals Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

2015 ◽  
Vol 11 ◽  
pp. 1865-1875 ◽  
Author(s):  
Biljana M Šmit ◽  
Radoslav Z Pavlović ◽  
Dejan A Milenković ◽  
Zoran S Marković
Keyword(s):  
Density Functional Theory ◽  
Double Bond ◽  
Density Functional ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Reaction Products ◽  
Dft Methods ◽  
Functional Theory ◽  
H Nmr ◽  
Good Agreement

The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of the internal nucleophile, the amidic nitrogen, to the seleniranium cation yielding the intermediate imidazolinium cations. Their deprotonation is followed by the formation of the fused bicyclic reaction products. Important intermediates and key transition states are studied by using density functional theory (DFT) methods. The pathways of the reaction are investigated in detail. There are two regioselective pathways related to 5-exo and 6-endo products. Theoretical calculations and the monitoring of the cyclization reaction using 1H NMR spectroscopy are in a good agreement with the proposed mechanism and are consistent with our experimental results. The preferred pathway for formation of 5-exo products is confirmed.

Sign in / Sign up

Export Citation Format

Share Document