scholarly journals Решеточная теплоемкость наноструктурированных материалов на основе титана/циркония и алюминия

2018 ◽  
Vol 60 (5) ◽  
pp. 835
Author(s):  
Е.Б. Долгушева ◽  
В.Ю. Трубицын
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Elastic Properties ◽  
Phonon Spectrum ◽  
Elastic Moduli ◽  
Aluminum Matrix ◽  
Method Of Molecular Dynamics ◽  
Densities Of States ◽  
Temperature Dependences

AbstractThe dynamic and thermal properties of nanostructured materials based on aluminum with the periodic inclusions of Ti or Zr clusters have been investigated by the method of molecular dynamics. The elastic moduli, spectral vibrational densities of states, and temperature dependences of heat capacity for different Ti–Al and Zr–Al systems have been obtained. The effect of specific features of the phonon spectrum on the heat capacity of the nanocomposite lattice has been examined. It is shown that the ordering type and size of Ti/Zr clusters in the aluminum matrix significantly affect the elastic properties and heat capacity. The results obtained can be used for fabricating new aluminum-, titanium-, and zirconium-based composites with the desired properties.

Study of elastic moduli and thermal properties of RMnO3 (R = La, Nd) compounds

2014 ◽  
Vol 03 (02) ◽  
pp. 1450011 ◽  
Author(s):  
Dinesh Varshney ◽  
Dinesh Choudhary
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Elastic Moduli ◽  
Systematic Investigation ◽  
Elastic Behavior ◽  
Repulsive Interaction ◽  
Interionic Interaction ◽  
Einstein Temperature ◽  
Capacity Calculation ◽  
Increasing Temperature

In this paper, we develop a theoretical model for quantitative analysis of temperature-dependent heat capacity calculation of the magnetoresistance compounds RMnO 3 ( R = La , Nd ). The results on heat capacity obtained by us are in good agreement with the measured values. An effective interionic interaction potential (EIoIP) with the long-range Coulomb, van der Waals (vdW) interaction and short-range repulsive interaction up to second neighbor ions within the Hafemeister and Flygare approach was formulated to estimate the Debye and Einstein temperature and was found to be consistent with the available experimental data. In addition, the properties studied are the cohesive energy, molecular force constant, Restrahlen frequency and Gruneisen parameter. After characterizing thermal properties, a systematic investigation of elastic behavior has been undertaken and it has been found that the elastic moduli are decreasing continuously with increasing temperature.

scholarly journals О термической устойчивости некоторых квазифуллеренов

2019 ◽  
Vol 61 (3) ◽  
pp. 604
Author(s):  
А.И. Подливаев ◽  
Л.А. Опенов
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Thermal Stability ◽  
Frequency Factor ◽  
Arrhenius Law ◽  
Method Of Molecular Dynamics ◽  
Temperature Dependences ◽  
Thermal Stability Of

AbstractThe thermal stability of recently predicted quasi-fullerenes С_20, С_42, С_48, and С_60 is studied by the method of molecular dynamics. The routes of their decomposition and the temperature dependences of their lifetimes are determined. The activation energy and frequency factor values that appear in the Arrhenius law are found. New isomers are detected.

scholarly journals CALCULATION OF THE THERMODYNAMIC CHARACTERISTICS OF Fe – P SYSTEM BY METHOD OF MOLECULAR DYNAMICS

2019 ◽  
Vol 62 (9) ◽  
pp. 725-731
Author(s):  
A. V. Markidonov ◽  
D. A. Lubyanoi ◽  
V. V. Kovalenko ◽  
M. D. Starostenkov
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Latent Heat ◽  
Linear Expansion ◽  
Computer Experiments ◽  
Theoretical Research ◽  
P System ◽  
Thermal Coefficient ◽  
Method Of Molecular Dynamics ◽  
Coefficient Of Linear Expansion

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal, require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependences of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure were established. Calculations showed that, for example, the phosphorus concentration of 0.5 % leads to an increase in the average thermal coefficient of linear expansion by 9 %, a decrease in temperature and latent heat of fusion by 5 % and a heat capacity by 7 %.

Modeling and Simulation of Thermophysical Properties of Minor Actinides-Containing Oxide Fuels

2007 ◽  
Vol 1043 ◽  
Author(s):  
Masahito Katayama ◽  
Jun Adachi ◽  
Ken Kurosaki ◽  
Masayoshi Uno ◽  
Shuhei Miwa ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Mixed Oxide ◽  
Perfect Crystal ◽  
Minor Actinide ◽  
Minor Actinides ◽  
Mox Fuel

AbstractThe molecular dynamics (MD) calculation was performed for minor actinide (MA: Np and Am)-containing mixed oxide (MOX) fuels, U0.7-xPu0.3MAxO2, in the temperature range from 300 to around 2500 K to evaluate the thermal expansion, heat capacity, and thermal conductivity. The MD results showed that the calculated heat capacity and thermal conductivity were similar in all the composition ranges, indicating that MA scarcely affected the thermal properties of the MOX fuel in the perfect crystal system.

Features of phonon spectra of CeO2, ThO2, NpO2 crystals due to the structure of their sublattices

2021 ◽  
Vol 64 (1) ◽  
pp. 50-57
Author(s):  
M.L. Zolotorev ◽  
◽  
A.S. Poplavnoi ◽  
T.P. Fedorova ◽  
I.A. Fedorov ◽  
...  
Keyword(s):  
Metal Ions ◽  
Phonon Spectrum ◽  
Low Energy ◽  
Spectral Lines ◽  
Phonon Spectra ◽  
Significant Difference ◽  
Densities Of States ◽  
Temperature Dependences

In CeO2, ThO2, and NpO2 crystals, the acoustic branches of the phonon spectrum correspond predominantly to the vibrations of metal ions, the optical ones mainly to the vibrations of the oxygen due to a significant difference in the mass values of these components of the compounds. An important crystallographic phenomena - metal and oxygen are located in sublattices corresponding to different Bravais types, which makes it possible to analyze vibrations in the corresponding Brillouin zones (BZ). This analysis was carried out by unfolding the optical branches of the phonon spectrum from the BZ of the crystal into the BZ of the oxygen sublatftice,the number of optical branches in this BZ is twice as small than in the BZ of the crystal. The effect of anharmonicity on the thermal broadening of the spectral lines of the phonon frequencies is studied in the approximation of two-phonon densities of states. The calculated two-phonon densities of states for all three compounds represent two broad structured peaks. The temperature dependences of the upper peak show the thermal broadening of the upper part of the optical branches, and the lower peak - low-energy optical and acoustic branches.

Elastic Properties of Cellulose by Molecular Dynamics Simulation

2013 ◽  
Vol 416-417 ◽  
pp. 1726-1730 ◽  
Author(s):  
Xiu Mei Zhang ◽  
Sheldon Q. Shi ◽  
Jun Cao
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Crystalline Cellulose ◽  
Internal Stresses ◽  
Molecular Models ◽  
Reactive Force

Molecular dynamics (MD) simulations were performed on molecular models of cellulose represented by two crystalline samples and amorphous samples. Simulated elastic properties and structures of each cellulose model were studied by MD simulations with the reactive force field and compared against experimental data for corresponding sample. The simulation boxes in stretch provide the materials elasticity. When there is a strain, the energy increases and internal stresses were built up within the supercell. The elastic moduli of amorphous and crystalline cellulose were comparable to the literature value. The calculated results had negligible difference with the experimentally measured parameters that indicated that the initial structures were stable using the ReaxFF.

scholarly journals Thermal properties of normal and sickled hemoglobin protein

BIBECHANA ◽  
2021 ◽  
Vol 18 (1) ◽  
pp. 140-148
Author(s):  
Jhulan Powrel ◽  
Narayan P Adhikari
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Root Mean Square ◽  
Specific Heat Capacity ◽  
Mean Square ◽  
Mean Square Deviation ◽  
Sickle Hemoglobin

Thermodynamic properties of sickled and normal hemoglobin protein are considered within the framework of classical molecular dynamics. Here we have studied the specific heat capacity and RMSD (Root Mean Square Deviation) of both types of hemoglobin protein. Our investigation reveals that the specific heat capacity and RMSD for oxygenated hemoglobin protein is higher than those of de-oxygenated sickle hemoglobin protein. It is also observed that the specific heat capacity and RMSD values of sickle hemoglobin protein decrease with a rise in temperature. BIBECHANA 18 (2021) 140-148

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

scholarly journals Testing a Gypsum Composite Based on Raw Gypsum with a Direct Admixture of Paraffin and Polymer to Improve Thermal Properties

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3241
Author(s):  
Krzysztof Powała ◽  
Andrzej Obraniak ◽  
Dariusz Heim
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Phase Change ◽  
Large Scale ◽  
Building Materials ◽  
Residential Buildings ◽  
Energy Performance ◽  
Polymer Content ◽  
Volumetric Heat Capacity

The implemented new legal regulations regarding thermal comfort, the energy performance of residential buildings, and proecological requirements require the design of new building materials, the use of which will improve the thermal efficiency of newly built and renovated buildings. Therefore, many companies producing building materials strive to improve the properties of their products by reducing the weight of the materials, increasing their mechanical properties, and improving their insulating properties. Currently, there are solutions in phase-change materials (PCM) production technology, such as microencapsulation, but its application on a large scale is extremely costly. This paper presents a solution to the abovementioned problem through the creation and testing of a composite, i.e., a new mixture of gypsum, paraffin, and polymer, which can be used in the production of plasterboard. The presented solution uses a material (PCM) which improves the thermal properties of the composite by taking advantage of the phase-change phenomenon. The study analyzes the influence of polymer content in the total mass of a composite in relation to its thermal conductivity, volumetric heat capacity, and diffusivity. Based on the results contained in this article, the best solution appears to be a mixture with 0.1% polymer content. It is definitely visible in the tests which use drying, hardening time, and paraffin absorption. It differs slightly from the best result in the thermal conductivity test, while it is comparable in terms of volumetric heat capacity and differs slightly from the best result in the thermal diffusivity test.

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