scholarly journals First-Principle Studies of the Vibrational Properties of Carbonates under Pressure

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3644
Author(s):  
Yurii N. Zhuravlev ◽  
Victor V. Atuchin
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Low Frequency ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Lattice Constants ◽  
Atomic Displacements ◽  
Carbonate Ion ◽  
The Density Functional Theory ◽  
Out Of Plane

Using the density functional theory with the hybrid functional B3LYP and the basis of localized orbitals of the CRYSTAL17 program code, the dependences of the wavenumbers of normal long-wave ν vibrations on the P(GPa) pressure ν(cm−1) = ν0 + (dv/dP)·P + (d2v/dP2)·P and structural parameters R(Å) (R: a, b, c, RM-O, RC-O): ν(cm−1) = ν0 + (dv/dR) − (R − R0) were calculated. Calculations were made for crystals with the structure of calcite (MgCO3, ZnCO3, CdCO3), dolomite (CaMg(CO3)2, CdMg(CO3)2, CaZn(CO3)2) and aragonite (SrCO3, BaCO3, PbCO3). A comparison with the experimental data showed that the derivatives can be used to determine the P pressures, a, b, c lattice constants and the RM-O metal-oxygen, and the RC-O carbon-oxygen interatomic distances from the known Δν shifts. It was found that, with the increasing pressure, the lattice constants and distances R decrease, and the wavenumbers increase with velocities the more, the higher the ν0 is. The exceptions were individual low-frequency lattice modes and out-of-plane vibrations of the v2-type carbonate ion, for which the dependences are either nonlinear or have negative dv/dP (positive dv/dR) derivatives. The reason for this lies in the properties of chemical bonding and the nature of atomic displacements during these vibrations, which cause a decrease in RM-O and an increase in RC-O.

Lattice dynamics of Ferroelectric TlInS2 crystal

2012 ◽  
Vol 90 (5) ◽  
pp. 407-412 ◽  
Author(s):  
K.R. Allakhverdiev ◽  
F.M. Hashimzade ◽  
D.A. Huseinova ◽  
M.A. Nizametdinova ◽  
G.S. Orudzhev ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Density Functional ◽  
Structural Parameters ◽  
Plane Waves ◽  
Low Frequency ◽  
Equilibrium Structure ◽  
Functional Theory ◽  
Lattice Constants ◽  
Pseudopotential Approach ◽  
Structure Calculations

In this paper we present the results of ab initio first-principle calculations of the lattice dynamics of ternary TlInS2 semiconductor with highly anisotropic crystal structure. Calculations have been performed using the open-source code ABINIT on the basis of density functional theory within the plane-wave pseudopotential approach. The basis of plane waves was truncated at electron kinetic energy of 40 Ha. Integration over the Brillouin zone was carried out using a 2 × 2 × 2 grid. The equilibrium structure was determined by minimizing the total energy with respect to the lattice constants and the internal structural parameters. The results are discussed in terms of previously existing experimental data. It is shown that along the layer, the low-frequency acoustic branch displays the bending wave behavior that is typical for crystals having a layered structure.

scholarly journals First-Principles Study of Mechanical and Thermodynamic Properties of Binary and Ternary CoX (X = W and Mo) Intermetallic Compounds

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1404
Author(s):  
Yunfei Yang ◽  
Changhao Wang ◽  
Junhao Sun ◽  
Shilei Li ◽  
Wei Liu ◽  
...  
Keyword(s):  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Vibrational Entropy ◽  
Functional Theory ◽  
Lattice Constants ◽  
The Density Functional Theory ◽  
Ductile Behavior ◽  
Pseudo Potential

In this study, the structural, elastic, and thermodynamic properties of DO19 and L12 structured Co3X (X = W, Mo or both W and Mo) and μ structured Co7X6 were investigated using the density functional theory implemented in the pseudo-potential plane wave. The obtained lattice constants were observed to be in good agreement with the available experimental data. With respect to the calculated mechanical properties and Poisson’s ratio, the DO19-Co3X, L12-Co3X, and μ-Co7X6 compounds were noted to be mechanically stable and possessed an optimal ductile behavior; however, L12-Co3X exhibited higher strength and brittleness than DO19-Co3X. Moreover, the quasi-harmonic Debye–Grüneisen approach was confirmed to be valid in describing the temperature-dependent thermodynamic properties of the Co3X and Co7X6 compounds, including heat capacity, vibrational entropy, and Gibbs free energy. Based on the calculated Gibbs free energy of DO19-Co3X and L12-Co7X6, the phase transformation temperatures for DO19-Co3X to L12-Co7X6 were determined and obtained values were noted to match well with the experiment results.

Investigations of the Optical Properties of LaNi5 and LaNi4.5Sn0.5

2013 ◽  
Vol 321-324 ◽  
pp. 495-498 ◽  
Author(s):  
Dong Chen ◽  
Chao Xu
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Optical Properties ◽  
Density Functional ◽  
Low Frequency ◽  
Potential Method ◽  
Frequency Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Pseudo Potential

The reflectivity, loss function, refractive index, extinction coefficient and dielectric function of the LaNi5and LaNi4.5Sn0.5intermetallic compounds are investigated through the plane-wave pseudo-potential method based on the density functional theory. The effects of Sn impurity are discussed and some interesting features are found in the low frequency region. Some important optical properties such as static dielectric constant and static refractive index are obtained. The equation [n (0)]2=ε1(0)is satisfied according to our calculation, which indicates that our results are correct and reasonable. Nevertheless, the calculated results need to be testified in the future due to the lack of experimental data.

Newly Determined Crystal Structure and Optical Property of the Intermetallic NiAl and Ni3Al Alloys: A First-Principles Computer Simulated Investigation

2014 ◽  
Vol 989-994 ◽  
pp. 220-223
Author(s):  
Chao Xu ◽  
Dong Chen
Keyword(s):  
Dielectric Function ◽  
Loss Function ◽  
First Principles ◽  
Density Functional ◽  
Peak Height ◽  
Functional Theory ◽  
Lattice Constants ◽  
Light Region ◽  
The Density Functional Theory ◽  
Lower Energy Region

Using quantum mechanics plane-wave approach based on the density functional theory, the lattice constants of NixAl at different Ni concentrations (x=1, 3) are predicted. Optical properties such as dielectric function, energy loss function and reflectivity are also investigated. Results show that with the increase of Ni constituent, the location of the peak in loss function moves to the lower energy region, but the peak height increases. At 0eV, the reflectivity increases rapidly with the Ni concentration. The reflectivity of NiAl and Ni3Al are pronounced in the UV region (not in the visible light region). The dielectric properties, namely the real and imaginary parts of the dielectric function, changed significantly with Ni constituent.

Tunable Magnetism and Half-Metallic Stability in Si-Doped Hg2CuTi-Type Ti2CoGa Alloy

2012 ◽  
Vol 229-231 ◽  
pp. 130-133 ◽  
Author(s):  
Bo Wu ◽  
Yu Feng ◽  
Hong Kuan Yuan ◽  
Hong Chen
Keyword(s):  
Density Functional ◽  
Magnetic Moments ◽  
Half Metallicity ◽  
Functional Theory ◽  
Half Metallic ◽  
Lattice Constants ◽  
Indirect Exchange ◽  
The Density Functional Theory ◽  
Si Doped ◽  
Direct Hybridization

Using the ab-initio calculations within the density functional theory (DFT), we have investigated the electronic structure, magnetism and half-metallic stability of Si-doped Heusler compound Ti2CoGa with Hg2CuTi-type structure. The results revel that the lattice constants and total magnetic moments in per unit obey the Vegard’s rule and the Slater-Pauling rule well, respectively. The most stable half-metallicity occurs at doping concentration x=0.75 because the Fermi level is located at the middle of the spin-minority gap. Our studies also indicate that the competition between RKKY-type indirect exchange and direct hybridization of d-electronic atoms plays a dominating role in determining the magnetism.

scholarly journals Structural and piezoelectric coefficients of AlP under pressure

2018 ◽  
Vol 6 (2) ◽  
pp. 53
Author(s):  
Salah Daoud ◽  
Rabie Mezouar ◽  
Abdelfateh Benmakhlouf
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Generalized Gradient ◽  
Aluminum Phosphide ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Zinc Blende ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory

The present work aims to investigate the structural parameters and the piezoelectric coefficients of cubic zinc-blende Aluminum phosphide (AlP) under high pressure up to 21 GPa, using plane wave-pseudopotential (PW-PP) approach in the framework of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the generalized gradient approximation (GGA) for the exchange-correlation functional. The results obtained are analyzed and compared with other data of the literature. The structural parameters and the piezoelectric coefficients calculated here agree well with other data of the literature. We found also that both the direct and converse piezoelectric coefficients increase with increasing pressure up to 21 GPa. 

Structural, optoelectronic and elastic properties of quaternary perovskites CaPd3B4O12 (B = Ti, V)

2019 ◽  
Vol 33 (19) ◽  
pp. 1950212 ◽  
Author(s):  
Shahid Mehmood ◽  
Zahid Ali ◽  
Zainab Hashmi ◽  
Sahar Khan
Keyword(s):  
Density Functional ◽  
Dielectric Material ◽  
Structural Parameters ◽  
Wide Bandgap ◽  
Spin Orbit Coupling ◽  
Hybrid Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Reported Data

Perovskites CaPd3B4O[Formula: see text] (B = Ti, V) are studied theoretically using generalized gradient approximation (GGA), GGA-modified Becke–Johnson (GGA-mBJ), GGA with spin-orbit coupling (GGA + SOC) and hybrid functional (HF) in the domain of density functional theory (DFT). The estimated structural parameters are reliable with the experimentally reported data. Cohesive energy and enthalpy show that these compounds are stable thermodynamically. Bonding nature makes known that the chemical bond between Ca/Ti–O is ionic, Pd/V–O is covalent and Ti/V–Ti/V is metallic. The mechanical properties show that these compounds are stable, elastically anisotropic and ductile in nature. CaPd3Ti4O[Formula: see text] is a 2.94 eV direct-wide bandgap semiconductor through GGA-mBJ and consistent with experiments. The optical properties show that CaPd3Ti4O[Formula: see text] is a good dielectric material. The dense electronic states and the wide-gap semiconductor nature of CaPd3Ti4O[Formula: see text] suggest that it can be used as a good thermoelectric material.

Theoretical analysis of ammoniaborane and alkylammoniaborane at the solid state

2017 ◽  
Author(s):  
Mariano Méndez Chávez
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Theoretical Analysis ◽  
Gas Phase ◽  
Density Functional ◽  
Structural Parameters ◽  
Ammonia Borane ◽  
Functional Theory ◽  
The Density Functional Theory

This work deals with a benchmark for the calculation of the structural parameters of ammonia-borane and alkylammonia-borane at the solid state, using hybrid and GGA functionals in the framework of the Density Functional Theory as well as the use of Grimme's empirical dispersion. A comparison for some dimers of the aforementioned species, calculated at the gas-phase at the level MP2/aug-cc-pVTZ is discussed.

scholarly journals Comprehensive Density Functional Theory Studies of Vibrational Spectra of Carbonates

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2275
Author(s):  
Yurii N. Zhuravlev ◽  
Victor V. Atuchin
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Predictive Power ◽  
Hybrid Functional ◽  
Program Code ◽  
Functional Theory ◽  
Carbonate Solutions ◽  
The Density Functional Theory ◽  
Bending Mode ◽  
Cation Radius

Within the framework of the density functional theory (DFT) and the hybrid functional B3LYP by means of the CRYSTAL17 program code, the wavenumbers and intensities of normal oscillations of MgCO3, CaCO3, ZnCO3, CdCO3 in the structure of calcite; CaMg(CO3)2, CdMg(CO3)2, CaMn(CO3)2, CaZn(CO3)2 in the structure of dolomite; BaMg(CO3)2 in the structure of the norsethite type; and CaCO3, SrCO3, BaCO3, and PbCO3 in the structure of aragonite were calculated. Infrared absorption and Raman spectra were compared with the known experimental data of synthetic and natural crystals. For lattice and intramolecular modes, linear dependences on the radius and mass of the metal cation are established. The obtained dependences have predictive power and can be used to study solid carbonate solutions. For trigonal and orthorhombic carbonates, the linear dependence of wavenumbers on the cation radius RM (or M–O distance) is established for the infrared in-plane bending mode: 786.2–65.88·RM and Raman in-plane stretching mode: 768.5–53.24·RM, with a correlation coefficient of 0.87.

scholarly journals Influence of water on the surface of graphene

2018 ◽  
Vol 174 ◽  
pp. 06002
Author(s):  
Yunus Kaya ◽  
Yalçin Kalkan ◽  
Rob Veenhof
Keyword(s):  
Density Functional Theory ◽  
Water Molecule ◽  
Density Functional ◽  
Theoretical Models ◽  
Surface Conductivity ◽  
Basis Set ◽  
Hybrid Functional ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Influence Of Water

We have studied how water modifies the surface of graphene and in particular how the surface conductivity of graphene is affected. According to the literature, two types of interactions should be distinguished: physical, where a water molecule remains intact and is located at some distance from the mesh, and chemical, where a water molecule is imbricated in the graphene bond structure. We have developed theoretical models for both types of interactions using the density functional theory (DFT) with the B3LYP hybrid functional combined with the 6-31G(d) basis set. Our calculations show that the surface conductivity of graphene is reduced in the presence of water.

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