Thermodynamic and thermoelastic properties of wurtzite-ZnS by density functional theory

2020 ◽  
Vol 105 (8) ◽  
pp. 1212-1222 ◽  
Author(s):  
Gianfranco Ulian ◽  
Daniele Moro ◽  
Giovanni Valdrè
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Mechanical Stability ◽  
Phonon Dispersion ◽  
Industrial Applications ◽  
Third Order ◽  
Functional Theory ◽  
Static Conditions ◽  
Good Agreement ◽  
Piezoelectric Constants

Abstract In the present paper, we provide a detailed theoretical investigation on fundamental thermodynamic, thermomechanical, and electronic properties of wurtzite ZnS between 0–20 GPa and 0–2000 K, obtained by ab initio density functional theory and the B3LYP functional. Several properties, such as phonon dispersion relations, elastic and piezoelectric constants, and thermodynamic and thermoelastic behaviors were calculated and reported. The analysis of the data via volume-integrated third-order Birch-Murnaghan fitting resulted in K0 = 72.17(4) GPa, K′ = 3.87(1), and V0 = 85.781(1) Å3 at T = 0 K. The Born criteria for the mechanical stability of the mineral phase showed that wurtzite is unstable above about 19 GPa in static conditions. We calculated a direct bandgap for wz-ZnS of 4.86 eV at zero compression, which became an indirect one by increasing pressure above 17 GPa. The results are in good agreement with the experimental and theoretical ones reported in the literature, and further extend the knowledge of an important zinc sulfide phase, for both geological and industrial applications.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

Study of dynamic and thermodynamic properties of zinc-blend and wurtzite cadmium sulfide (CdS) using density functional theory

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Teshome Gerbaba Edossa ◽  
Menberu Mengasha Woldemariam
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Density Functional ◽  
Chemical Potential ◽  
Phonon Dispersion ◽  
Dynamic Properties ◽  
Dielectric Constants ◽  
High Symmetry ◽  
Functional Theory ◽  
Zinc Blend

Abstract The dynamic and thermodynamic properties of wurtzite (wz) and zinc-blend (zb) CdS are investigated within the density functional theory using different approximation methods such as LDA, PBE, and DFT+U. Hellmann–Feynman approach is implemented for the relaxation of atomic position for both phases. To guarantee the accuracy of calculation, the convergence test of total energy with respect to energy cutoff and k-point sampling is performed. The dynamic properties such as phonon dispersion, phonon density of state, frequency along with high symmetry points, static and dynamic polarizability, and dielectric constants are calculated. The obtained values are compared with previous theoretical results. DFT + U approximation gives a good result that is consistent with the available theory. Moreover, the vibrational energy, vibrational free energy, entropy, electron chemical potential, and constant-volume specific heat are obtained within LDA, PBE, and DFT + U approximations.

Electric Field Gradient in Aluminium due to Vacancy and Muon

1992 ◽  
Vol 47 (1-2) ◽  
pp. 45-48
Author(s):  
M. J. Ponnambalam
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
Density Functional ◽  
Near Neighbour ◽  
Electric Field Gradients ◽  
Functional Theory ◽  
Field Gradients ◽  
Analytic Expression ◽  
Valence Effect ◽  
Good Agreement

AbstractThe electric field gradients (EFG) in aluminium due to a monovacancy and the interstitial muon are evaluated. The valence effect EFG qv is calculated using perturbed electron density δn(r)values obtained from density functional theory in an analytic expression which is valid at all distances from the impurity. The size effect EFG qs is evaluated using a new oscillatory form for the near neighbour (nn) displacements. The numerical values of qs are computed using fractional nn displacements available in the literature. For the total EFG good agreement with experiment is obtained without the use of any parameter.

scholarly journals The Pseudopotential Approach within Density-Functional Theory: The Case of Atomic Metallic Hydrogen

2020 ◽  
Vol 5 (4) ◽  
pp. 74
Author(s):  
Jin Zhang ◽  
Jeevake Attapattu ◽  
Jeffrey M. McMahon
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Metallic Phase ◽  
Metallic Hydrogen ◽  
Spectral Functions ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Pseudopotential Approach ◽  
Critical Temperature Tc

Internal energies, enthalpies, phonon dispersion curves, and superconductivity of atomic metallic hydrogen are calculated. The standard use of pseudopotentials in density-functional theory are compared with full Coulomb-potential, all-electron linear muffin-tin orbital calculations. Quantitatively similar results are found as far as internal energies are concerned. Larger differences are found for phase-transition pressures; significant enough to affect the phase diagram. Electron–phonon spectral functions α2F(ω) also show significant differences. Against expectation, the estimated superconducting critical-temperature Tc of the first atomic metallic phase I41/amd (Cs-IV) at 500 GPa is actually higher.

scholarly journals Analysis of vibratinal spectra of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives based on density functional theory calculations

2007 ◽  
Vol 5 (1) ◽  
pp. 201-220 ◽  
Author(s):  
Khaled Bahgat ◽  
Abdel Ragheb
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Basis Set ◽  
Normal Coordinate ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Vibrational Bands ◽  
Good Agreement

AbstractThe geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives were obtained by the density functional theory (DFT) calculations with Becke3-Lee-Parr (B3LYP) functional and 6-31G* basis set. The effects of chloride, bromide, iodide and nitro substituent on the vibrational frequencies of 8-hydroxyquinoline have been investigated. The assignments have been proposed with aid of the results of normal coordinate analysis. The observed and calculated spectra are found to be in good agreement.

Density Functional Theory Study: Interactions of Lithium-Montmorillonite with Poly(Ethylene Oxide) as Preliminary Investigation of Lithium Polymer Conductivity

2014 ◽  
Vol 893 ◽  
pp. 790-793
Author(s):  
Muhammad Naufal Lintangpradipto ◽  
Triati Dewi Kencana Wungu ◽  
Ahmad H. Lubis ◽  
Hermawan Kresno Dipojono ◽  
Nugraha
Keyword(s):  
Density Functional Theory ◽  
Ethylene Oxide ◽  
Potential Energy ◽  
Density Functional ◽  
Preliminary Investigation ◽  
Energy Curve ◽  
Functional Theory ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Good Agreement

In this study, the interactions between poly (ethylene oxide) (PEO) and lithium-montmorillonite (LiMMT) have been investigated using density functional theory (DFT) calculation. The results of calculations show that the adsorption process of PEO on the LiMMT surface is physisorption with adsorption energy of -0.063 eV. This observation is consistent with the results of our calculations on PES (Potential Energy Surface) and PEC (Potential Energy Curve). The formation of space between PEO and LiMMT are found in range of 3.4 - 4.2 Å which are in good agreement with experimental results.

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