Structural, elasto-mechanical and phonon-related properties of MnCrP: A DFT Study

2020 ◽  
Vol 34 (21) ◽  
pp. 2050200
Author(s):  
A. Afaq ◽  
Abu Bakar ◽  
Muhammad Shoaib ◽  
Rashid Ahmed ◽  
Anila Asif
Keyword(s):  
Mechanical Stability ◽  
Phonon Dispersion ◽  
Structural Parameters ◽  
Far Infrared ◽  
Phonon Modes ◽  
Phonon Dispersion Curves ◽  
Anisotropic Factor ◽  
Cauchy Pressure ◽  
The Stability ◽  
Thermal Vibrations

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants [Formula: see text], [Formula: see text] and [Formula: see text]. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.

Two-phonon absorption in InSb, InAs, and GaAs

1976 ◽  
Vol 54 (16) ◽  
pp. 1676-1682 ◽  
Author(s):  
E. S. Koteles ◽  
W. R. Datars
Keyword(s):  
Phonon Dispersion ◽  
Inelastic Neutron Scattering ◽  
Far Infrared ◽  
Inelastic Neutron ◽  
Model Fit ◽  
Fourier Transform Spectrometer ◽  
Phonon Density ◽  
Phonon Dispersion Curves ◽  
Phonon Absorption ◽  
Good Agreement

Far-infrared absorption in the III–V compound semiconductors InSb, InAs, and GaAs has been measured using a Fourier transform spectrometer. The high-resolution spectra of the three materials were found to be very similar. Features on the spectra were assigned to two-phonon sum and difference processes with the aid of two-phonon density-of-states curves for InSb and GaAs calculated from a shell model fit to phonon dispersion curves. Interpretation of the spectrum of InAs was possible because of its similarity to that of InSb and GaAs. The frequencies of phonons at certain points in the Brillouin zone of InSb and GaAs determined from the mode assignments to the infrared spectra were in good agreement with previous measurements by inelastic neutron scattering and Raman scattering.

scholarly journals Lattice dynamics in CePd2Al2 and LaPd2Al2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Petr Doležal ◽  
Petr Cejpek ◽  
Satoshi Tsutsui ◽  
Koji Kaneko ◽  
Dominik Legut ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Elastic Interaction ◽  
Bound State ◽  
Dispersion Curves ◽  
Phonon Modes ◽  
Phonon Dispersion Curves ◽  
X Ray Scattering ◽  
Oppenheimer Approximation ◽  
Good Agreement

AbstractThe interaction between phonons and 4f electrons, which is forming a new quantum state (quasi-bound state) beyond Born-Oppenheimer approximation, is very prominent and lattice dynamics plays here a key role. There is only a small number of compounds in which the experimental observation suggest such a scenario. One of these compounds is CePd2Al2. Here the study of phonon dispersion curves of (Ce,La)Pd2Al2 at 1.5, 7.5, 80 and 300 K is presented. The inelastic X-ray scattering technique was used for mapping the phonon modes at X and Z points as well as in Λ and Δ directions, where the symmetry analysis of phonon modes was performed. The measured spectra are compared with the theoretical calculation, showing very good agreement. The measurements were performed in several Brillouin zones allowing the reconstruction of phonon dispersion curves. The results are discussed with respect to the magneto-elastic interaction and are compared with other cerium compounds. The phonon mode symmetry A1g was found to be unaffected by the interaction, which is in contrast to previous assumptions.

Computational Study of Ru2TiZ (Z = Si, Ge, Sn) for Structural, Mechanical and Vibrational Properties

2019 ◽  
Vol 74 (6) ◽  
pp. 545-550
Author(s):  
Aneeza Iftikhar ◽  
A. Afaq ◽  
Iftikhar Ahmad ◽  
Abu Bakar ◽  
H. Bushra Munir ◽  
...  
Keyword(s):  
Elastic Constants ◽  
Phonon Dispersion ◽  
Computational Study ◽  
Heusler Alloys ◽  
Vibrational Properties ◽  
Mechanical Parameters ◽  
Phonon Modes ◽  
Lattice Constants ◽  
The Stability ◽  
Experimental Values

AbstractThe structural, mechanical and vibrational properties of Ru2TiZ (Z = Si, Ge, Sn) Full Heusler Alloys (FHAs) are computed using PBE-GGA as an exchange-correlation functional in Kohn–Sham equations. The calculated lattice constants of these alloys in L21 phase deviate from experimental values upto 0.85 % which shows a good agreement between the model and the experiments. These lattice constants are then used to compute the second order elastic constants C11, C12 and C44 with Wien2k-code. Elastic moduli and mechanical parameters are also calculated by these three independent elastic constants. Mechanical parameters Pugh’s and Poisson’s ratio indicate non-brittle nature of these alloys. Furthermore, the Debye temperature where the collective vibrations shift to an independent thermal vibration, longitudinal and transverse sound velocities, melting temperatures, and thermal conductivities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of these alloys as there exists no imaginary phonon frequency in the phonon-dispersion curves.

Temperature-dependent X-ray dynamical diffraction: Darwin theory simulations

1999 ◽  
Vol 55 (1) ◽  
pp. 14-19 ◽  
Author(s):  
Jin-Seok Chung ◽  
Stephen M. Durbin
Keyword(s):  
Phonon Dispersion ◽  
Lattice Vibrations ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Phonon Dispersion Curves ◽  
Dynamical Diffraction ◽  
X Ray ◽  
Ergodic Hypothesis ◽  
Thermal Vibrations ◽  
Good Agreement

Thermal vibrations destroy the perfect crystalline periodicity generally assumed by dynamical diffraction theories. This can lead to some difficulty in deriving the temperature dependence of X-ray reflectivity from otherwise perfect crystals. This difficulty is overcome here in numerical simulations based on the extended Darwin theory, which does not require periodicity. Using Si and Ge as model materials, it is shown how to map the lattice vibrations derived from measured phonon dispersion curves onto a suitable Darwin model. Good agreement is observed with the usual Debye–Waller behavior predicted by standard theories, except at high temperatures for high-order reflections. These deviations are discussed in terms of a possible breakdown of the ergodic hypothesis for X-ray diffraction.

scholarly journals Phonon dynamics of Zr67Ni33 AND Fe80B20 binary glassy alloys

BIBECHANA ◽  
2021 ◽  
Vol 18 (1) ◽  
pp. 33-47
Author(s):  
Aditya M Vora ◽  
Alkesh L Gandhi
Keyword(s):  
Amorphous Alloys ◽  
Phonon Dispersion ◽  
Phonon Modes ◽  
Phonon Dispersion Curves ◽  
Pseudopotential Theory ◽  
Glassy Alloys ◽  
Phonon Dynamics ◽  
Different Temperatures ◽  
Alloy Atom ◽  
Acceptable Agreement

Binary amorphous alloys are the primary bulk metallic glasses (BMGs). Two binary BMGs Zr67Ni33 and Fe80B20 have been studied in the present work using the pseudo- alloy-atom (PAA) model based on the pseudopotential theory. Some important thermodynamic properties like Debye temperature and elastic properties like elasticity moduli and Poisson’s ratio at room temperature are theoretically computed with the help of pseudopotential theory from the elastic limit of the phonon dispersion curves (PDCs). The collective dynamics of longitudinal and transverse phonon modes are investigated in terms of eigenfrequencies of the localized collective modes. The presently computed results are compared with the other such data including theoretically generated results from the molecular dynamics at different temperatures as available in the literature and an acceptable agreement is found. BIBECHANA 18 (2021) 33-47 

scholarly journals Phase Stability of the Tin Monochalcogenides SnS and SnSe: A Quasi-Harmonic Lattice-Dynamics Study

2021 ◽  
Author(s):  
Ioanna Pallikara ◽  
Jonathan Skelton
Keyword(s):  
Lattice Dynamics ◽  
Potential Energy Surfaces ◽  
Phonon Dispersion ◽  
Free Energies ◽  
Phonon Modes ◽  
Elastic Band ◽  
Phonon Dispersion Curves ◽  
Potential Applications ◽  
Band Method ◽  
Energy Surfaces

The tin monochalcogenides SnS and SnSe adopt four different crystal structures, <i>viz.</i> orthorhombic <i>Pnma</i> and <i>Cmcm</i> and cubic rocksalt and π-cubic (P2<sub>1</sub>3) phases, each of which has optimal properties for a range of potential applications. This rich phase space makes it challenging to identify the conditions under which the different phases are obtained. We have performed first-principles quasi-harmonic lattice-dynamics calculations to assess the relative stabilities of the four phases of SnS and SnSe. We investigate dynamical stability through the presence or absence of imaginary modes in the phonon dispersion curves, and we compute Helmholtz and Gibbs free energies to evaluate the thermodynamic stability. We also consider applied pressures from 0-15 GPa to obtain temperature-pressure phase diagrams. Finally, the relationships between the different crystal phases are investigated by explicitly mapping the potential-energy surfaces along the imaginary phonon modes and by using the climbing-image nudged elastic-band method.

scholarly journals Phase Stability of the Tin Monochalcogenides SnS and SnSe: A Quasi-Harmonic Lattice-Dynamics Study

2021 ◽  
Author(s):  
Ioanna Pallikara ◽  
Jonathan Skelton
Keyword(s):  
Lattice Dynamics ◽  
Potential Energy Surfaces ◽  
Phonon Dispersion ◽  
Free Energies ◽  
Phonon Modes ◽  
Elastic Band ◽  
Phonon Dispersion Curves ◽  
Potential Applications ◽  
Band Method ◽  
Energy Surfaces

The tin monochalcogenides SnS and SnSe adopt four different crystal structures, <i>viz.</i> orthorhombic <i>Pnma</i> and <i>Cmcm</i> and cubic rocksalt and π-cubic (P2<sub>1</sub>3) phases, each of which has optimal properties for a range of potential applications. This rich phase space makes it challenging to identify the conditions under which the different phases are obtained. We have performed first-principles quasi-harmonic lattice-dynamics calculations to assess the relative stabilities of the four phases of SnS and SnSe. We investigate dynamical stability through the presence or absence of imaginary modes in the phonon dispersion curves, and we compute Helmholtz and Gibbs free energies to evaluate the thermodynamic stability. We also consider applied pressures from 0-15 GPa to obtain temperature-pressure phase diagrams. Finally, the relationships between the different crystal phases are investigated by explicitly mapping the potential-energy surfaces along the imaginary phonon modes and by using the climbing-image nudged elastic-band method.

scholarly journals Thermal Transport of Flexural and In-Plane Phonons Modulated by Bended Graphene Nanoribbons

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Changning Pan ◽  
Jun He ◽  
Diwu Yang ◽  
Keqiu Chen
Keyword(s):  
Low Temperature ◽  
Transport Properties ◽  
Thermal Transport ◽  
Phonon Dispersion ◽  
Graphene Nanoribbons ◽  
Structural Parameters ◽  
Thermal Conductance ◽  
Phonon Modes ◽  
Thermal Transport Properties ◽  
Out Of Plane

Ballistic thermal transport properties are investigated comparatively for out-of-plane phonon modes (FPMs) and in-plane phonon modes (IPMs) in bended graphene nanoribbons (GNRs). Results show that the phonon modes transports can be modulated separately by the phonon dispersion mismatch between armchair and zigzag GNRs in considered system. The contribution of FPMs to total thermal conductance is larger than 50% in low temperature for perfect GNRs. But it becomes less than 20% in the bended GNRs. Furthermore, this contribution can be modulated by changing the structural parameters of the bended GNRs. The result is useful for the design of thermal or thermoelectric nanodevices in future.

The Pressure Dependence of Structural, Electronic, Mechanical, Vibrational, and Thermodynamic Properties of Palladium-Based Heusler Alloys

2017 ◽  
Vol 72 (9) ◽  
pp. 843-853 ◽  
Author(s):  
Cansu Çoban
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constants ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Heusler Alloys ◽  
Dispersion Curves ◽  
Pressure Derivative ◽  
Electronic Band ◽  
Phonon Dispersion Curves ◽  
The Stability

AbstractThe pressure dependent behaviour of the structural, electronic, mechanical, vibrational, and thermodynamic properties of Pd2TiX (X=Ga, In) Heusler alloys was investigated by ab initio calculations. The lattice constant, the bulk modulus and its first pressure derivative, the electronic band structure and the density of states (DOS), mechanical properties such as elastic constants, anisotropy factor, Young’s modulus, etc., the phonon dispersion curves and phonon DOS, entropy, heat capacity, and free energy were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature, the elastic constants obey the stability criterion, and the phonon dispersion curves have no negative frequency which shows that the compounds are stable. The band structures at 0, 50, and 70 GPa showed valence instability at the L point which explains the superconductivity in Pd2TiX (X=Ga, In).

Phonons in chiral nanorods and nanotubes: A Cosserat-rod-based continuum approach

2019 ◽  
Vol 24 (12) ◽  
pp. 3897-3919
Author(s):  
Prakhar Gupta ◽  
Ajeet Kumar
Keyword(s):  
Phonon Dispersion ◽  
Coefficient Matrix ◽  
Molecular Data ◽  
Dispersion Curves ◽  
Mode Shapes ◽  
Wave Form ◽  
Phonon Modes ◽  
Continuum Approach ◽  
Phonon Dispersion Curves ◽  
Cosserat Rod

A Cosserat-rod-based continuum approach is presented to obtain phonon dispersion curves of flexural, torsional, longitudinal, shearing, and radial breathing modes in chiral nanorods and nanotubes. Upon substituting the continuum wave form in the linearized dynamic equations of stretched and twisted Cosserat rods, we obtain an analytical expression of a coefficient matrix (in terms of the rod’s stiffnesses, induced axial force, and twisting moment) whose eigenvalues and eigenvectors give us frequencies and mode shapes, respectively, for each of the above phonon modes. We show that, unlike the case of achiral tubes, these phonon modes are intricately coupled in chiral tubes owing to extension–torsion–inflation and bending–shear couplings inherent in them. This coupling renders the conventional approach of obtaining stiffnesses from the long wavelength limit slope of dispersion curves redundant. However, upon substituting the frequencies and mode shapes (obtained independently from phonon dispersion molecular data) in the eigenvalue–eigenvector equation of the above-mentioned coefficient matrix, we are able to obtain all the stiffnesses (bending, twisting, stretching, shearing, and all coupling stiffnesses corresponding to extension–torsion, extension–inflation, torsion–inflation, and bending–shear couplings) of chiral nanotubes. Finally, we show unusual effects of the single-walled carbon nanotube’s chirality as well as stretching and twisting of the nanotube on its phonon dispersion curves obtained from the molecular approach. These unusual effects are accurately reproduced in our continuum formulation.

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