scholarly journals Elastic constants and optical phonon frequencies of BX (X= P, As, and Sb) semiconductors: Semi-empirical prediction

2020 ◽  
Vol 8 (2) ◽  
pp. 45
Author(s):  
Salah Daoud ◽  
Pawan Kumar Saini ◽  
Hamza Rekab-Djabri
Keyword(s):  
Elastic Constants ◽  
Longitudinal Optical ◽  
Group Iv ◽  
Boron Compounds ◽  
Empirical Formulas ◽  
Empirical Prediction ◽  
Lattice Constants ◽  
Zinc Blende ◽  
Semi Empirical ◽  
Good Agreement

Based on some simple empirical formulas established by Adachi in, Properties of group-IV, III-V and II-VI semiconductors, John Wiley & Sons, Chichester (2005), and the experimental lattice constants reported in the literature; the present work aims to predict the elastic constants and some other significant properties of cubic zinc-blende boron compounds (BP, BAs and BSb). The obtained values of C12and C44 are in general good agreement with other data of the literature, while C11 and B are slightly lower. The zone-center longitudinal optical (LO) and transverse optical (TO) phonon frequencies are also obtained. The LO and TO phonon frequencies of BP compound were found at 866.6and 834.5 cm–1, respectively; these of BAs were found at 731.3 and 727.1 cm–1, respectively; while for the BSb narrow-gap semiconducting compound were found at around 598.3and 586.2 cm–1, respectively. These two later values are in general slightly lower than the calculated values, and the observed Raman spectroscopy values reported in the literature. 

STRUCTURAL PHASE TRANSITION IN BORON COMPOUNDS AT HIGH PRESSURE

2010 ◽  
Vol 24 (10) ◽  
pp. 1235-1244 ◽  
Author(s):  
MINA TALATI ◽  
PRAFULLA K. JHA
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Elastic Constants ◽  
Structural Phase ◽  
Boron Compounds ◽  
Potential Approach ◽  
Transition Pressure ◽  
Zinc Blende ◽  
Phase Transition Pressure ◽  
Good Agreement

The high-pressure induced structural phase transitions and pressure induced elastic and anharmonic behavior of boron compounds viz. BN, BP, and BAs have been investigated using an inter-ionic potential approach based on charge transfer effect. These compounds go to NaCl phase (B1) under pressure from zinc blende phase (B3). The variations of second-order elastic constants and their combinations follow a systematic trend with pressure, identical to that observed in other compounds of zinc blende structure family. Shear stiffness constants decrease with increasing pressure up to phase transition pressure. The bulk moduli of these compounds are in reasonably good agreement with other theoretical and experimental data. The values of phase transition pressure of these compounds obtained by using the present approach are also in good agreement with those predicted by using the pseudo potential approach. The present approach has also succeeded in predicting the Born and relative stability criterion for stable zinc blende phase of these compounds. We also present a set of third-order elastic constants and pressure derivatives of second-order elastic constants for boron compounds.

First Principle Study of Ti50Al50 Alloys

2018 ◽  
Vol 770 ◽  
pp. 224-229
Author(s):  
Rosinah Modiba ◽  
Hasani Chauke ◽  
Phuti Ngoepe
Keyword(s):  
Experimental Data ◽  
High Temperatures ◽  
Elastic Constants ◽  
Martensitic Phase ◽  
First Principle ◽  
Lattice Constants ◽  
B2 Phase ◽  
Experimental Values ◽  
Good Agreement

The study on the Ti-based materials and its application has been the interest of many research industries. These alloys are known to have an ordered B2 phase at high temperatures and transform to a stable low B19 martensitic phase. First principle approach has been used to study L10, B32, B2 and B19 Ti50Al50alloys and the results compared well with the available experimental data. The equilibrium lattice constants are in good agreement with the experimental values (within 3% agreement). Furthermore, the elastic constants of these alloys are calculated, and revealed stability for L10and B19 structures, while B2 and B32 gave C′<0 (condition of instability).

First Principles Study of Electronic and Elastic Properties of AlY

2014 ◽  
Vol 1047 ◽  
pp. 45-50
Author(s):  
Mani Shugani ◽  
Mahendra Aynyas ◽  
S.P. Sanyal
Keyword(s):  
Elastic Properties ◽  
Elastic Constants ◽  
Ground State ◽  
Full Potential ◽  
Augmented Plane Wave ◽  
Plane Wave Method ◽  
Lattice Constants ◽  
Ground State Properties ◽  
Experimental Values ◽  
Good Agreement

We have used full potential linear augmented plane wave method within thegeneralized gradient approximation to investigate the structural, electronic and elastic properties of the AlY. The ground state properties are determined for the AlY. The calculated ground state properties such as lattice constants, bulk modulus and elastic constants agree well with the experimental values. From band structure curves it is found that AlY is metallic in nature. The elastic constants are in good agreement with previous theoretical and experimental results.

Structural and Mechanical Properties of RT2Zn20 and RFe2-xCoxZn20(R=Y, Sm; T=Fe, Ru, Os, Co, Rh and Ir)

2011 ◽  
Vol 689 ◽  
pp. 204-210 ◽  
Author(s):  
Yi Chen ◽  
Jiang Shen
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Mechanical Properties ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
Interatomic Potentials ◽  
Lattice Constants ◽  
Quaternary Compounds ◽  
Cohesive Energies ◽  
Good Agreement

The phase stability, crystal structure and mechanical properties of YT2Zn20 and SmT2Zn20 (T=Fe, Ru, Os, Co, Rh and Ir) compounds have been investigated by using interatomic potentials based on the lattice inversion technique. The calculated lattice constants are in good agreement with the experimental data. The lattice constants increase and Bulk modulus decrease as the transition metal T varies from 3d to 5d. The Y-based compounds with lower energies are more stable than the Sm analogs. Also, the Bulk modulus of YT2Zn20 series are larger than SmT2Zn20 series. Moreover, the mechanical properties of the quaternary compounds YFe2-xCoxZn20 and SmFe2-xCoxZn20­, such as the elastic constants and bulk modulus, have been calculated in this work. The substitution of Co atoms would decrease the cohesive energies and increase the bulk modulus of materials.

Indirekte Kernspinkopplung in den Tetramethylverbindungen der IV. Gruppe

1967 ◽  
Vol 22 (9) ◽  
pp. 1458-1464 ◽  
Author(s):  
Herbert Dreeskamp ◽  
Gerhard Stegmeier
Keyword(s):  
Double Resonance ◽  
Group Iv ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Group Iv Elements ◽  
Semi Empirical ◽  
Spin Spin Coupling ◽  
Contact Mechanism ◽  
Good Agreement

The indirect nuclear spin-spin coupling between protons, C13 and the spin ½ isotopes of the group IV elements (Si29, Sn119 and Pb207) were investigated in the tetramethylcompounds X(CH3)4. Substances enriched in C13 were used. The absorption of the most sensitive nucleus H1 was observed directly while the resonances of the other nuclei were located by a double resonance technique. The normalized coupling constants between directly bonded nuclei were found to be positive in all cases while their magnitudes are in good agreement with a semi-empirical estimate using the contact mechanism. All normalized two-bond X—C—H coupling constants are negative while the three-bond C—X—C—H coupling constants are positive as well as the four-bond H—C—Si—C—H coupling constant. Using these results it is shown that the sign of the normalized X—H coupling constants in the analogous hydrides XH4 are positive confirming a theoretical prediction made in previous work.

The crystal dynamics of cuprous halides

1982 ◽  
Vol 60 (11) ◽  
pp. 1589-1594 ◽  
Author(s):  
Manvir S. Kushwaha
Keyword(s):  
Phonon Dispersion ◽  
Characteristic Temperature ◽  
Force Model ◽  
Phonon Dispersion Curves ◽  
Debye Characteristic Temperature ◽  
Zinc Blende ◽  
Crystal Dynamics ◽  
Bond Bending ◽  
Dynamical Description ◽  
Good Agreement

The lattice dynamics of cuprous halides have been thoroughly investigated by means of an 8-parameter bond-bending force model (BBFM), recently developed and applied successfully to study phonons in various II–VI and III–V compound semiconductors having zinc-blende (ZB) structure. The application of BBFM is made to calculate the phonon dispersion relations, phonon density of states, and temperature variation of the Debye characteristic temperature [Formula: see text] of CuCl, CuBr, and CuI. The room-temperature neutron scattering measurements for phonon dispersion curves along three principal symmetry directions and calorimetric experimental data for the Debye characteristic temperature have been used to check the validity of BBFM for the three crystals. The overall good agreement between theoretical and experimental results supports its use as an appropriate model for the dynamical description of ZB crystals.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

Semi-Empirical Crest Distributions of Long-Crest Nonlinear Waves of Three-Hour Duration

2017 ◽  
Author(s):  
Zhenjia (Jerry) Huang ◽  
Qiuchen Guo
Keyword(s):  
Nonlinear Wave ◽  
Wave Height ◽  
Model Test ◽  
Significant Wave Height ◽  
Spectral Peak ◽  
Wave Crest ◽  
Empirical Formulas ◽  
Peak Period ◽  
Significant Wave ◽  
Semi Empirical

In wave basin model test of an offshore structure, waves that represent the given sea states have to be generated, qualified and accepted for the model test. For seakeeping and stationkeeping model tests, we normally accept waves in wave calibration tests if the significant wave height, spectral peak period and spectrum match the specified target values. However, for model tests where the responses depend highly on the local wave motions (wave elevation and kinematics) such as wave impact, green water impact on deck and air gap tests, additional qualification checks may be required. For instance, we may need to check wave crest probability distributions to avoid unrealistic wave crest in the test. To date, acceptance criteria of wave crest distribution calibration tests of large and steep waves of three-hour duration (full scale) have not been established. The purpose of the work presented in the paper is to provide a semi-empirical nonlinear wave crest distribution of three-hour duration for practical use, i.e. as an acceptance criterion for wave calibration tests. The semi-empirical formulas proposed in this paper were developed through regression analysis of a large number of fully nonlinear wave crest distributions. Wave time series from potential flow simulations, computational fluid dynamics (CFD) simulations and model test results were used to establish the probability distribution. The wave simulations were performed for three-hour duration assuming that they were long-crested. The sea states are assumed to be represented by JONSWAP spectrum, where a wide range of significant wave height, peak period, spectral peak parameter, and water depth were considered. Coefficients of the proposed semi-empirical formulas, comparisons among crest distributions from wave calibration tests, numerical simulations and the semi-empirical formulas are presented in this paper.

Structural, Electronic, and Mechanical Properties of CoN and NiN: An Ab Initio Study

2017 ◽  
Vol 72 (4) ◽  
pp. 321-330 ◽  
Author(s):  
A. Amudhavalli ◽  
M. Manikandan ◽  
A. Jemmy Cinthia ◽  
R. Rajeswarapalanichamy ◽  
K. Iyakutti
Keyword(s):  
Elastic Constants ◽  
Electronic Structures ◽  
Elastic Anisotropy ◽  
Structural Phase ◽  
Lattice Parameter ◽  
Stable Phase ◽  
Ab Initio Study ◽  
Zinc Blende ◽  
Experimental Values ◽  
Parameter Values

AbstractThe structural stabilities of cobalt mononitride (CoN) and nickel mono-nitride (NiN) were investigated among the crystal structures, namely, NaCl (B1), CsCl (B2), and zinc blende (B3). It was found that the zinc blende (B3) phase was the most stable phase for both nitrides. A pressure-induced structural phase transition from B3 to B1 phase was predicted in these nitrides. The computed lattice parameter values were in agreement with the experimental values and other theoretical values. The electronic structures reveal that these nitrides are metallic at zero pressure. The computed elastic constants indicate that CoN and NiN are mechanically stable in the B1 and B3 phases. The variations of the elastic constants, bulk modulus, shear modulus, Poisson’s ratio, and elastic anisotropy factor with pressure were investigated. The Debye temperature θD values are reported for both the nitrides in their B1 and B3 phases. The high-pressure NaCl phase of both CoN and NiN were found to be ferromagnetic.

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