scholarly journals BARIC DEPENDENCE OF LATTICE PROPERTIES FOR DIAMOND

2018 ◽  
Vol 59 (9) ◽  
pp. 57
Author(s):  
Makhach N. Magomedov
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Elastic Modulus ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Interatomic Potential ◽  
State Equation ◽  
Relative Volume ◽  
Lennard Jones ◽  
Good Agreement

Based on the pairwise interatomic potential of Mi-Lennard-Jones and the Einstein's model of crystal the state equation P(V/V0, T) and the baric dependencies of the lattice properties for diamond were obtained. The calculations were performed along two isotherms: T = 300 and 3000 K and until to P = 10000 kbar (i.e. until to the relative volume V/V0 = 0.5). The baric dependencies for the following properties were obtained: isothermal elastic modulus, isochoric and isobaric heat capacities and thermal expansion coefficient. Good agreement with experimental data was obtained.

SIZE AND TEMPERATURE EFFECT ON THERMAL EXPANSION COEFFICIENT AND LATTICE PARAMETER OF NANOMATERIALS

2013 ◽  
Vol 27 (25) ◽  
pp. 1350180 ◽  
Author(s):  
RAGHUVESH KUMAR ◽  
GEETA SHARMA ◽  
MUNISH KUMAR
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Temperature Dependence ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Size Dependence ◽  
Coefficient Of Thermal Expansion ◽  
Lattice Parameter ◽  
Model Predictions ◽  
Good Agreement

A simple theoretical model is developed to study the effect of size and temperature on the coefficient of thermal expansion and lattice parameter of nanomaterials. We have studied the size dependence of thermal expansion coefficient of Pb , Ag and Zn in different shape viz. spherical, nanowire and nanofilm. A good agreement between theory and available experimental data confirmed the model predictions. We have used these results to study the temperature dependence of lattice parameter for different size and also included the results of bulk materials. The temperature dependence of lattice parameter of Zn nanowire and Ag nanowire are found to present a good agreement with the experimental data. We have also computed the temperature and size dependence of lattice parameter of Se and Pb for different shape viz. spherical, nanowire and nanofilm. The results are discussed in the light of recent research on nanomaterials.

scholarly journals Метод определения параметров парного межатомного потенциала

2020 ◽  
Vol 62 (7) ◽  
pp. 998
Author(s):  
М.Н. Магомедов
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Interatomic Potential ◽  
Coefficient Of Thermal Expansion ◽  
State Equation ◽  
Zero Temperature ◽  
Thermoelastic Properties ◽  
Lennard Jones ◽  
Sublimation Energy ◽  
Potential Parameters

Disadvantages of methods known from the literature for determining 4 parameters of the paired interatomic potential of Mie-Lennard-Jones in relation to crystals are indicated. A new method is proposed for determining the parameters of this potential from the thermoelastic properties of the crystal. In this method the parameters are determined by the best coincidence of calculated values with experimental data: 1) of the sublimation energy of the crystal at zero temperature (T = 0 K) and pressure (P = 0); 2) of coefficient of thermal expansion and isothermal elastic modulus, which were measured at P = 0 and T = 300 K; 3) of the dependence of the isotherm T = 300 K state equation from volume of P(300 K, V). The method was tested on iron and gold and showed good results. By this method also were determined the interatomic potential parameters for refractory metals: Nb, Ta, Mo, and W. The results obtained also made it possible to determine more precisely such properties of these metals as the sublimation energy, the Debye temperature, and the surface energy.

Equation of State of α-Al2O3 (Corundum) from Quasi-Harmonic Atomistic Simulations

1998 ◽  
Vol 54 (6) ◽  
pp. 741-749 ◽  
Author(s):  
M. Catti ◽  
A. Pavese
Keyword(s):  
Thermal Expansion ◽  
Bulk Modulus ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Interatomic Potential ◽  
Unit Cell ◽  
Atomistic Simulations ◽  
Ambient Conditions ◽  
Thermal Dependence ◽  
Α Al2o3

A two-body interatomic potential function, including fractional atomic charges and a shell model for oxygen, and supplemented by an O—Al—O bond-angle energy term, was fitted to the structural, elastic and vibrational properties of \alpha-Al2O3, corundum, at ambient conditions. Full quasi-harmonic calculations were then carried out on a p,T grid of 54 points in the domain 0–40 GPa and 300–1700 K. The crystal structure was equilibrated at each point, taking into account the anisotropy of vibrational pressure and the thermal dependence of elastic constants, so as to obtain unit-cell edges, atomic coordinates, bulk modulus, thermal expansion coefficient and other thermodynamic properties. Polynomial approximations were developed to represent the p,T dependence of these quantities. Comparison with experimental results for the separate p (T = 300 K) and T (p = 0) behaviours shows very good agreement, with average deviations of 0.1% for the unit-cell volume and 6% for the thermal expansion coefficient. The coupled p,T dependence of the properties of corundum is predicted to be very small for the bulk modulus (\partial^2K_T/\partial p\partial T=8.4\times10^{-5} K−1), but not at all negligible for the volume [(1/V)\partial^2V/\partial p\partial T in the range −1.2 to −7.5 × 10−7 GPa−1 K−1 over the p,T domain explored].

ANHARMONIC EFFECTIVE POTENTIAL, LOCAL FORCE CONSTANT AND EXAFS OF HCP CRYSTALS: THEORY AND COMPARISON TO EXPERIMENT

2008 ◽  
Vol 22 (29) ◽  
pp. 5155-5166 ◽  
Author(s):  
NGUYEN VAN HUNG ◽  
TONG SY TIEN ◽  
LE HAI HUNG ◽  
RONALD R. FRAHM
Keyword(s):  
Thermal Expansion ◽  
Fine Structure ◽  
Thermal Expansion Coefficient ◽  
Force Constant ◽  
Expansion Coefficient ◽  
Effective Potential ◽  
X Ray ◽  
X Ray Absorption ◽  
Analytical Expressions ◽  
Good Agreement

Anharmonic effective potential, Extended X-ray Absorption Fine Structure (EXAFS) and its parameters of hcp crystals have been theoretically and experimentally studied. Analytical expressions for the anharmonic effective potential, effective local force constant, three first cumulants, a novel anharmonic factor, thermal expansion coefficient and anhamonic contributions to EXAFS amplitude and phase have been derived. This anharmonic theory is applied to analyze the EXAFS of Zn and Cd at 77 K and 300 K, measured at HASYLAB (DESY, Germany). Numerical results are found to be in good agreement with experiment, where unnegligible anharmonic effects have been shown in the considered theoretical and experimental quantities.

scholarly journals Изучение свойств сплава золото-железо в макро- и нанокристаллических состояниях в различных P-T-условиях

2020 ◽  
Vol 62 (12) ◽  
pp. 2034
Author(s):  
М.Н. Магомедов
Keyword(s):  
Surface Energy ◽  
Specific Surface ◽  
Interatomic Potential ◽  
State Equation ◽  
Specific Surface Energy ◽  
Lennard Jones ◽  
Pressure Region ◽  
Substitution Alloy ◽  
Fe Substitution ◽  
Good Agreement

For a disordered fcc-Au-Fe substitution alloy, the parameters of the Mie–Lennard-Jones pairwise interatomic potential are determined. Based on these parameters, the concentration dependencies of lattice properties for the macrocrystal of this alloy are calculated. Calculations of 20 properties of macrocrystals fcc-Au, fcc-Fe and fcc-Au0.5Fe0.5 are showed good agreement with experimental data. Using the RP-model of the nanocrystal, the state equation P(v, T; N) and baric dependences of both lattice and surface properties of the fcc-Au0.5Fe0.5 alloy are calculated. Calculations were performed at temperatures T = 100, 300 and 500 K for both a macrocrystal (N = Macro) and a cubic nanocrystal with N = 306 atoms. It is shown that with an isothermal-isobaric (P = 0) decrease in the size of a nanocrystal, its the Debye temperature, elastic modulus, and specific surface energy decrease, while its the specific volume, thermal expansion coefficient, specific heat capacity, and Poisson's ratio increase. At low temperatures in a certain pressure region, the specific surface energy increases at an isothermal-isobaric decrease in the number of atoms in the nanocrystal. As the temperature increases, this pressure region disappears.

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