scholarly journals Optoelectronic, thermodynamic and vibrational properties of intermetallic MgAl2Ge2: a first-principles study

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
A. M. M. Tanveer Karim ◽  
M. A. Helal ◽  
M. A. Alam ◽  
M. A. Ali ◽  
I. Ara ◽  
...  
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Surface Topology ◽  
Ultraviolet Region ◽  
Vibrational Properties ◽  
Optical Parameters ◽  
Lattice Instability ◽  
Brillouin Zone Boundary ◽  
Functional Theory ◽  
Electron Charge Density

AbstractIntermetallic compounds with CaAl2Si2-type structure have been studied extensively due to their exciting set of physical properties. Among various alumo-germanides, MgAl2Ge2 is the new representative of CaAl2Si2-type structures. Our previous study explores the structural aspects, mechanical behaviors and electronic features of intermetallic MgAl2Ge2. The present work discloses the results of optoelectronic, thermodynamic and vibrational properties of MgAl2Ge2 via density functional theory-based investigations. The band structure calculations suggest that MgAl2Ge2 possesses slight electronic anisotropy and the compound is metallic. The Fermi surface topology reveals that both electron- and hole-like sheets are present in MgAl2Ge2. The electron charge density map indicates toward the dominance of covalent bonding in MgAl2Ge2. The optical parameters are found to be independent of the state of the polarization of incident electric field. The large value of the reflectivity in the visible-to-ultraviolet region up to ~ 15 eV suggests that MgAl2Ge2 might be a good candidate as coating material to avoid solar heating. The thermodynamic properties have been calculated using the quasi-harmonic Debye approximation. We have found indications of lattice instability at the Brillouin zone boundary in the trigonal $$P\overline{3}m1$$ P 3 ¯ m 1 phase from the phonon dispersion curves. However, the compound might be stable at elevated temperature and as a function of pressure. All the theoretical findings herein have been compared with the reported results (where available). Various implications of our results have been discussed in detail. Graphic abstract

Computational investigations of MnNiCuSb alloy for structural, elasto-mechanical and vibrational properties

2019 ◽  
Vol 33 (23) ◽  
pp. 1950276
Author(s):  
Abu Bakar ◽  
Maaz Afzal ◽  
Muzaffar Bashir ◽  
A. Afaq ◽  
Aneeza Iftikhar ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dispersion Curve ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Phonon Dispersion Curve ◽  
Vibrational Properties ◽  
Type I ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Anisotropic Factor

The MnNiCuSb Quaternary Heusler Alloy (QHA) in Y-type I stable structure (cubic) is studied for structural, elastic, mechanical and vibrational properties by using Density Functional Theory (DFT). Three independent elastic constants [Formula: see text], [Formula: see text] and [Formula: see text] for this cubic system are computed with Generalized Gradient Approximation (GGA) functional. The mechanical parameters like Young’s modulus, Shear and Bulk modulus, Pugh’s ratio, Poisson’s ratio, anisotropic factor, Cauchy pressure are then calculated by using these cubic elastic parameters. In addition, phonon dispersion curve and phonon density of states (PDOS) are computed with norm-conserving Martins–Troullier pseudo-potential in Perturbed Density Functional Theory. The phonon dispersion curve provides reststrahlen band 0.727 THz [Formula: see text] for which material behaves as 100%. This value corresponds to Far Infra-Red (FIR) spectral region so this alloy can be used for manufacturing FIR-devices.

Ab initio study of optical and vibrational properties of Ni3C

2017 ◽  
Vol 31 (03) ◽  
pp. 1750003
Author(s):  
Mohammad Bagher Golivand ◽  
Arash Boochani ◽  
Arsalan Akhtar ◽  
Maryam Torkashvand ◽  
Nashmyl Karimian
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Energy Gap ◽  
Structural Parameters ◽  
Infrared Region ◽  
Vibrational Properties ◽  
Optical Parameters ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Good Agreement

The structural, electronic, optical and vibrational properties of Ni3C have been studied by density functional theory (DFT) framework with first-principles study. The obtained structural parameters are in good agreement with other works. The electronic study demonstrates metallic behavior of Ni3C since it has no energy gap at Fermi level. The optical parameters such as real and imaginary dielectric functions, loss function, conductivity, reflection, refraction indexes and absorption coefficients are studied. The phonon investigations confirm that the Ni3C bulk is dynamically stable and carbon has a major role in optical spectrum of the material at infrared region. Finally, the [Formula: see text] behavior of [Formula: see text] at low temperatures is obtained, as expected.

scholarly journals Compression Behavior and Vibrational Properties of New Energetic Material LLM-105 Analyzed Using the Dispersion-Corrected Density Functional Theory

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6831
Author(s):  
Tianming Li ◽  
Junyu Fan ◽  
Zhuoran Wang ◽  
Hanhan Qi ◽  
Yan Su ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
High Pressure ◽  
Uniaxial Compression ◽  
Density Functional ◽  
Structural Parameters ◽  
Energetic Material ◽  
Structure Stability ◽  
Vibrational Properties ◽  
Detailed Knowledge ◽  
Functional Theory

The 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is a newly energetic material with an excellent performance and low sensitivity and has attracted considerable attention. On the basis of the dispersion-corrected density functional theory (DFT-D), the high-pressure responses of vibrational properties, in conjunction with structural properties, are used to understand its intermolecular interactions and anisotropic properties under hydrostatic and uniaxial compressions. At ambient and pressure conditions, the DFT-D scheme could reasonably describe the structural parameters of LLM-105. The hydrogen bond network, resembling a parallelogram shape, links two adjacent molecules and contributes to the structure stability under hydrostatic compression. The anisotropy of LLM-105 is pronounced, especially for Raman spectra under uniaxial compression. Specifically, the red-shifts of modes are obtained for [100] and [010] compressions, which are caused by the pressure-induced enhance of the strength of the hydrogen bonds. Importantly, coupling modes and discontinuous Raman shifts are observed along [010] and [001] compressions, which are related to the intramolecular vibrational redistribution and possible structural transformations under uniaxial compressions. Overall, the detailed knowledge of the high-pressure responses of LLM-105 is established from the atomistic level. Uniaxial compression responses provide useful insights for realistic shock conditions.

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.

Influence of Pressure on Structural, Optical and Electronic Properties of As-ZnO

2019 ◽  
Vol 807 ◽  
pp. 110-114
Author(s):  
Ling Ping Xiao ◽  
Yun Qin Liu ◽  
Li Zeng
Keyword(s):  
Optical Properties ◽  
Valence Band ◽  
Density Functional ◽  
Optical Constants ◽  
First Principles Calculations ◽  
Band Shift ◽  
Functional Theory ◽  
Electron Charge Density ◽  
Optical And Electronic Properties ◽  
Doped Zno

First-principles calculations are performed to study the electronic structures and optical properties of the As-doped ZnO under pressure up to 8 GPa. After doped, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of As-doped ZnO to increase the charge overlap between atoms. Moreover, as the pressure increases, the conduction and valence band shift to lower and higher energies, respectively. The shifts of the conduction and valence band result in a decreasing band gap. Additionally, the calculated optical constants of As-doped ZnO under pressure are also presented. Keywords: high pressure; As-doped ZnO; optical properties, Density functional theory.

scholarly journals Structural, Electronic and Vibrational Properties of YAl3(BO3)4

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 545 ◽  
Author(s):  
Aleksandr S. Oreshonkov ◽  
Evgenii M. Roginskii ◽  
Nikolai P. Shestakov ◽  
Irina A. Gudim ◽  
Vladislav L. Temerov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Band Gap ◽  
Density Functional ◽  
Dielectric Material ◽  
Electronic Band Structure ◽  
Vibrational Properties ◽  
Electronic Band ◽  
Functional Theory ◽  
Dynamical Properties ◽  
Indirect Band Gap

The crystal structure of YAl3(BO3)4 is obtained by Rietveld refinement analysis in the present study. The dynamical properties are studied both theoretically and experimentally. The experimental Raman and Infrared spectra are interpreted using the results of ab initio calculations within density functional theory. The phonon band gap in the Infrared spectrum is observed in both trigonal and hypothetical monoclinic structures of YAl3(BO3)4. The electronic band structure is studied theoretically, and the value of the band gap is obtained. It was found that the YAl3(BO3)4 is an indirect band gap dielectric material.

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