Lattice Dynamical Prediction of the Elastic Constants of Diamond

1996 ◽  
Vol 453 ◽  
Author(s):  
Robert R. Reeber
Keyword(s):  
Equation Of State ◽  
Elastic Constants ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Interatomic Potential ◽  
Dynamical Theory ◽  
Potential Models ◽  
Dimensional Lattice ◽  
One Dimensional ◽  
Metastable Material

AbstractThe thermophysical properties of diamond, a metastable material at room temperature, are difficult to measure at high temperatures. These properties are of interest for testing equation of state and interatomic potential models. Here we utilize a geometrical lattice transformation, one dimensional lattice dynamical theory, and the principle of corresponding states to calculate the elastic constants of diamond over an extended temperature range.

scholarly journals Numerical calculation of elastic properties of FCC crystals using molecular dynamics simulation

2021 ◽  
Author(s):  
Robert Szydlowski
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Elastic Constants ◽  
Interatomic Potential ◽  
Linear Thermal Expansion ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Potential Models ◽  
Embedded Atom

The elastic constants and the bulk modulus of six FCC monoatomic metals were calculated using molecular dynamics simulation as functions of temperature. In addition, the coefficients of linear thermal expansion were also calculated for all six metals. A fully functional 3D molecular dynamics code capable of simulating single crystals composed of one type of atom was written for this study. Eight different embedded-atom method (EAM) interatomic potential models were used to simulate the properties of the six metals. The elastic constants were calculated using fluctuation formulas which are functions of both potential energy, as well as the momentum of the particles in the system. It was found that the temperature dependence of elastic constants is not well exhibited by all EAM potentials. However, the eight EAM potentials presented in this study show results comparable to the values and trends of experimental data

scholarly journals Numerical calculation of elastic properties of FCC crystals using molecular dynamics simulation

2021 ◽  
Author(s):  
Robert Szydlowski
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Elastic Constants ◽  
Interatomic Potential ◽  
Linear Thermal Expansion ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Potential Models ◽  
Embedded Atom

The elastic constants and the bulk modulus of six FCC monoatomic metals were calculated using molecular dynamics simulation as functions of temperature. In addition, the coefficients of linear thermal expansion were also calculated for all six metals. A fully functional 3D molecular dynamics code capable of simulating single crystals composed of one type of atom was written for this study. Eight different embedded-atom method (EAM) interatomic potential models were used to simulate the properties of the six metals. The elastic constants were calculated using fluctuation formulas which are functions of both potential energy, as well as the momentum of the particles in the system. It was found that the temperature dependence of elastic constants is not well exhibited by all EAM potentials. However, the eight EAM potentials presented in this study show results comparable to the values and trends of experimental data

Mechanicals Behaviors of Tungsten-Rhenium Alloy Single Crystals from 77K to 300K - Atomic Simulation Study

2020 ◽  
Vol 50 ◽  
pp. 177-181
Author(s):  
Abdellah Tahiri ◽  
Mohamed Idiri ◽  
Brahim Boubeker
Keyword(s):  
Elastic Constant ◽  
Single Crystals ◽  
Elastic Constants ◽  
Room Temperature ◽  
Interatomic Potential ◽  
Calculation Model ◽  
Atomic Simulation ◽  
Rhenium Alloy ◽  
Embedded Method ◽  
Good Agreement

The elastic constants of tungsten-rhenium alloy single crystals were calculated by simulation atomic method using embedded method atom of interatomic potential. The found results show that elastic constants are proportional to the rhenium concentration up to 25 at% Re at room temperature. By following, we observed the elastic constant C44 dependency of temperature and decreased of elastic constant C’=1/2(C11-C12) when the Re atom addition increases. We have found that a growing instability of the bcc crystal structure. Our parameter calculation model is in good agreement with experimental data.

Pressure dependent ultrasonic properties of hcp hafnium metal

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ramanshu P. Singh ◽  
Shakti Yadav ◽  
Giridhar Mishra ◽  
Devraj Singh
Keyword(s):  
Elastic Constants ◽  
Pressure Range ◽  
Room Temperature ◽  
Ultrasonic Attenuation ◽  
Coupling Constants ◽  
Ultrasonic Properties ◽  
Acoustic Coupling ◽  
Third Order Elastic Constants ◽  
The Stability ◽  
The Given

Abstract The elastic and ultrasonic properties have been evaluated at room temperature between the pressure 0.6 and 10.4 GPa for hexagonal closed packed (hcp) hafnium (Hf) metal. The Lennard-Jones potential model has been used to compute the second and third order elastic constants for Hf. The elastic constants have been utilized to calculate the mechanical constants such as Young’s modulus, bulk modulus, shear modulus, Poisson’s ratio, and Zener anisotropy factor for finding the stability and durability of hcp hafnium metal within the chosen pressure range. The second order elastic constants were also used to compute the ultrasonic velocities along unique axis at different angles for the given pressure range. Further thermophysical properties such as specific heat per unit volume and energy density have been estimated at different pressures. Additionally, ultrasonic Grüneisen parameters and acoustic coupling constants have been found out at room temperature. Finally, the ultrasonic attenuation due to phonon–phonon interaction and thermoelastic mechanisms has been investigated for the chosen hafnium metal. The obtained results have been discussed in correlation with available findings for similar types of hcp metals.

Crystal structure of the anticancer drug carmustine determined by X-ray powder diffraction

2021 ◽  
pp. 1-3
Author(s):  
Carina Schlesinger ◽  
Edith Alig ◽  
Martin U. Schmidt
Keyword(s):  
Crystal Structure ◽  
Anticancer Drug ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Commercial Sample ◽  
One Dimensional ◽  
X Ray ◽  
Hydrogen Bond Pattern

The structure of the anticancer drug carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, C5H9Cl2N3O2) was successfully determined from laboratory X-ray powder diffraction data recorded at 278 K and at 153 K. Carmustine crystallizes in the orthorhombic space group P212121 with Z = 4. The lattice parameters are a = 19.6935(2) Å, b = 9.8338(14) Å, c = 4.63542(6) Å, V = 897.71(2) ų at 153 K, and a = 19.8522(2) Å, b = 9.8843(15) Å, c = 4.69793(6) Å, V = 921.85(2) ų at 278 K. The Rietveld fits are very good, with low R-values and smooth difference curves of calculated and experimental powder data. The molecules form a one-dimensional hydrogen bond pattern. At room temperature, the investigated commercial sample of carmustine was amorphous.

A new one-dimensional CdIIcoordination polymer with a two-dimensional layered structure incorporating 2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole and benzene-1,2-dicarboxylate ligands

2016 ◽  
Vol 72 (6) ◽  
pp. 480-484 ◽  
Author(s):  
Qiu-Ying Huang ◽  
Xiao-Yi Lin ◽  
Xiang-Ru Meng
Keyword(s):  
Layered Structure ◽  
Room Temperature ◽  
Weak Interactions ◽  
Coordination Geometry ◽  
Dimensional Chain ◽  
Two Dimensional ◽  
One Dimensional ◽  
Heterocyclic Ligand ◽  
Rich Variety ◽  
Solvent Molecules

The N-heterocyclic ligand 2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole (imb) has a rich variety of coordination modes and can lead to polymers with intriguing structures and interesting properties. In the coordination polymercatena-poly[[cadmium(II)-bis[μ-benzene-1,2-dicarboxylato-κ4O1,O1′:O2,O2′]-cadmium(II)-bis{μ-2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole}-κ2N2:N3;κ2N3:N2] dimethylformamide disolvate], {[Cd(C8H4O4)(C11H10N4)]·C3H7NO}n, (I), each CdIIion exhibits an irregular octahedral CdO4N2coordination geometry and is coordinated by four O atoms from two symmetry-related benzene-1,2-dicarboxylate (1,2-bdic2−) ligands and two N atoms from two symmetry-related imb ligands. Two CdIIions are connected by two benzene-1,2-dicarboxylate ligands to generate a binuclear [Cd2(1,2-bdic)2] unit. The binuclear units are further connected into a one-dimensional chain by pairs of bridging imb ligands. These one-dimensional chains are further connected through N—H...O hydrogen bonds and π–π interactions, leading to a two-dimensional layered structure. The dimethylformamide solvent molecules are organized in dimeric pairsviaweak interactions. In addition, the title polymer exhibits good fluorescence properties in the solid state at room temperature.

Polar Optical Phonon Instability and Intervalley Transfer in Gallium Nitride

1998 ◽  
Vol 512 ◽  
Author(s):  
B. E. Foutz ◽  
S. K. O'leary ◽  
M. S. Shur ◽  
L. F. Eastman ◽  
B. L. Gelmont ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Analytical Model ◽  
Optical Phonon ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Polar Optical Phonon ◽  
Scattering Mechanism ◽  
Loss Mechanism ◽  
One Dimensional ◽  
Optical Phonon Scattering

ABSTRACTWe develop a simple, one-dimensional, analytical model, which describes electron transport in gallium nitride. We focus on the polar optical phonon scattering mechanism, as this is the dominant energy loss mechanism at room temperature. Equating the power gained from the field with that lost through scattering, we demonstrate that beyond a critical electric field, 114 kV/cm at T = 300 K, the power gained from the field exceeds that lost due to polar optical phonon scattering. This polar optical phonon instability leads to a dramatic increase in the electron energy, this being responsible for the onset of intervalley transitions. The predictions of our analytical model are compared with those of Monte Carlo simulations, and are found to be in satisfactory agreement.

A time-dependent model for high-pressure discharges in narrow ablative capillaries

1993 ◽  
Vol 50 (1) ◽  
pp. 51-70 ◽  
Author(s):  
D. Zoler ◽  
S. Cuperman ◽  
J. Ashkenazy ◽  
M. Caner ◽  
Z. Kaplan
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Time Dependent ◽  
Dimensional Model ◽  
Plasma Sources ◽  
One Dimensional ◽  
Space And Time ◽  
Dependent Model ◽  
Energy Equations ◽  
Time Dependent Model

A time-dependent quasi-one-dimensional model is developed for studying high- pressure discharges in ablative capillaries used, for example, as plasma sources in electrothermal launchers. The main features of the model are (i) consideration of ablation effects in each of the continuity, momentum and energy equations; (ii) use of a non-ideal equation of state; and (iii) consideration of space- and time-dependent ionization.

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