Thermal Properties of Magnesium Hydroxide Using First-Principles Method

2012 ◽  
Vol 512-515 ◽  
pp. 609-612
Author(s):  
Qing Li Ren ◽  
Qiang Luo
Keyword(s):  
Thermal Properties ◽  
High Temperature ◽  
Debye Temperature ◽  
Magnesium Hydroxide ◽  
First Principles ◽  
Crystalline Powder ◽  
Powder Samples ◽  
Lattice Wave ◽  
Acoustic Lattice ◽  
First Principles Method

The thermal properties of the magnesium hydroxide crystalline powder samples, which were prepared by us, were investigated by first-principles method. The calculated results show that the forbidden band of phonon appears in both 14～19 THz and 33～102 THz. There are 3 acoustic lattice wave branches and 12 optical ones, where two horizontal acoustic branches are degeneracy and two horizontal optical ones are degeneracyhe. Moreover, The constant-volume specific heat quickly increases at low temperature; but it tends to be flat at high temperature. Besides, the Debye temperature quickly increases to 483K from temperature 0K to 10K; but from temperature 100K to 1000K, it is linear with temperature approximately, whose increasing rate is about 1.333; at temperature of 1000K, the Debye temperature is 1930K, reaching its maximum.

Optical Properties of Mg(OH)2 Using First-Principles Method

2011 ◽  
Vol 412 ◽  
pp. 427-431 ◽  
Author(s):  
Qing Li Ren ◽  
Qiang Luo ◽  
Yan Hong Hou
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Energy Loss ◽  
First Principles ◽  
Crystalline Powder ◽  
Static State ◽  
Value Range ◽  
Powder Samples ◽  
Peak Value ◽  
First Principles Method

The optical properties of the Mg (OH)2 crystalline powder samples, which were prepared by us, were investigated by first-principles method. The calculated results show that the static state dielectric function ε1(0) for Mg (OH)2 is 2.8673. The peak value range for the Mg (OH)2 absorption coefficient is mainly in the energy range from 45.521 eV to 66.0213 eV. Moreover, absorption coefficient researches its maximum, which is 1490460cm-1, at the energy of 63.7988eV. Besides, when energy is greater than 66.3901eV, the reflectivity rate is one. And the average static state refractive rate n (0) for Mg (OH)2 is 1.6292. While the maximum peak of energy loss function for Mg (OH)2 is in 20.4755eV.

scholarly journals First Principles Calculations on Elastic, Thermodynamic and Electronic Properties of Co2Zr and Co2Ti at High Temperature and Pressure

2020 ◽  
Vol 10 (6) ◽  
pp. 2097
Author(s):  
Mi-An Xue ◽  
Xiaoli Yuan ◽  
Cheng Zhong ◽  
Peng Wan
Keyword(s):  
High Temperature ◽  
Electronic Properties ◽  
Debye Temperature ◽  
First Principles ◽  
Density Functional ◽  
Debye Model ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

Co2Zr and Co2Ti are both cubic crystals with a Cu2Mg-type structure. The elastic, thermodynamic and electronic properties of the intermetallic compounds Co2Zr and Co2Ti are investigated by using ab initio plane-wave pseudopotential density functional theory (PWPDFT) and generalized gradient approximation (GGA) under high temperature and pressure. The partially calculated results are consistent with the available experimental data. The elastic properties of Co2Zr and Co2Ti under high pressure were first studied by first principles calculations. The results indicate that the elastic constants, elastic modulus and Poisson’s ratio are functions of pressure, indicating that the effect of pressure on the ductility and anisotropy is significant. The thermodynamic properties are also calculated by the quasi-harmonic Debye model. In the range of 0~100 GPa pressure and 0~1500 K temperature, the Debye temperature Θ, the heat capacity CV and the thermal expansion α vary with pressure and temperature. Co2Ti has a higher Debye temperature than Co2Zr under the same pressure. Decreasing temperature and increasing pressure have the same effects on CV and α. The electron density difference and density of states of Co2Zr and Co2Ti are finally investigated. The results show that both Co2Zr and Co2Ti are typically metal crystals but Co2Zr has greater covalence than Co2Ti.

scholarly journals Elastic Behavior of γ-Li3N under Pressure

2011 ◽  
Vol 3 (3) ◽  
pp. 569-574
Author(s):  
M. A. Hossain ◽  
A. K. M. A. Islam
Keyword(s):  
Debye Temperature ◽  
Elastic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Elastic Moduli ◽  
Gamma Transition ◽  
Elastic Behavior ◽  
Gamma Phase ◽  
First Time ◽  
First Principles Method

The elastic properties of gamma-Li3N have been studied for the first time by first-principles method. Three independent elastic constants, aggregate elastic moduli (B, G, E), Poisson’s ratio and Debye temperature are calculated as a function of pressure from 37.12 (beta to gamma transition value)  to 200 GPa and the implications of the results are discussed.Keywords: Li3N; Gamma-phase; Elastic properties; Debye temperature.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i3.7832               J. Sci. Res. 3 (3), 579-584 (2011)

First-principles investigation of the vacancy-related properties of Ta2AlC

2019 ◽  
Vol 33 (18) ◽  
pp. 1950209
Author(s):  
Jitao Liu ◽  
Zhaocang Meng ◽  
Jiajia Liu ◽  
Xiaolu Zhu ◽  
Canglong Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
First Principles ◽  
Formation Energy ◽  
Vacancy Formation ◽  
Clear Effect ◽  
Formation Energies ◽  
Nuclear Applications ◽  
First Principles Method

The formation energies and formation volumes of the Ta, Al, and C vacancies in Ta2AlC have been calculated by using first-principles method. The results have shown that the vacancy formation is energetically most favorable for the C atom with formation energy of 1.72 eV. The formation energies of Ta and Al vacancies are 3.44 eV and 3.52 eV, respectively. The electronics properties show that the Ta vacancy has a clear effect on the conductivity of the Ta2AlC. This result indicates that Ta2AlC is a good candidate material for high-temperature and nuclear applications.

Effect of Sc, Y, Yb, Hf, Ce on Mechanical and Thermal Properties of La2Zr2O7: First-Principles Calculations

2015 ◽  
Vol 1120-1121 ◽  
pp. 85-93 ◽  
Author(s):  
Lei Jin ◽  
Pei Zhong Li ◽  
Chun Zhu Jiang ◽  
Guo Dong Zhou ◽  
Hai Bin Zhou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Sound Velocity ◽  
Young’S Modulus ◽  
Debye Temperature ◽  
Elastic Constants ◽  
First Principles ◽  
Young's Modulus ◽  
Elastic Stiffness ◽  
Mechanical And Thermal Properties

In order to achieve better understanding of the effect of dopant (Sc, Y, Yb, Hf and Ce) on elastic stiffness and thermal properties of La2Zr2O7. The related calculations were performed using the first principles methods. The predicted elastic constants indicate that La2Zr2O7 and oxidations-La2Zr2O7 (oxidations refer to Sc2O3, Y2O3, Yb2O3, HfO2 and CeO2) are mechanically stable structures. And then the numerical estimates of bulk modulus, shear modulus, Young’s modulus were performed using the calculated elastic constants. After these mechanical properties are obtained, sound velocity, Debye temperature and theoretical minimum thermal conductivity of La2Zr2O7 and oxidations-La2Zr2O7 are calculated and analyzed in detail. The available experimental results and our calculations are basically satisfactory. The calculated results indicate that Young’s modulus, mean sound velocity, Debye temperature and minimum thermal conductivity of La2Zr2O7 can be decreased by dopants. CeO2 has extraordinary ability to decrease thermal conductivity in these dopant oxidations.

scholarly journals Demonstration of Phase Change Thermal Energy Storage in Zinc Oxide Microencapsulated Sodium Nitrate

2021 ◽  
Vol 11 (13) ◽  
pp. 6234
Author(s):  
Ciprian Neagoe ◽  
Ioan Albert Tudor ◽  
Cristina Florentina Ciobota ◽  
Cristian Bogdanescu ◽  
Paul Stanciu ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Thermal Properties ◽  
High Temperature ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Sodium Nitrate ◽  
Thermal Energy Storage ◽  
Metal Corrosion ◽  
Scanning Calorimetry

Microencapsulation of sodium nitrate (NaNO3) as phase change material for high temperature thermal energy storage aims to reduce costs related to metal corrosion in storage tanks. The goal of this work was to test in a prototype thermal energy storage tank (16.7 L internal volume) the thermal properties of NaNO3 microencapsulated in zinc oxide shells, and estimate the potential of NaNO3–ZnO microcapsules for thermal storage applications. A fast and scalable microencapsulation procedure was developed, a flow calorimetry method was adapted, and a template document created to perform tank thermal transfer simulation by the finite element method (FEM) was set in Microsoft Excel. Differential scanning calorimetry (DSC) and transient plane source (TPS) methods were used to measure, in small samples, the temperature dependency of melting/solidification heat, specific heat, and thermal conductivity of the NaNO3–ZnO microcapsules. Scanning electron microscopy (SEM) and chemical analysis demonstrated the stability of microcapsules over multiple tank charge–discharge cycles. The energy stored as latent heat is available for a temperature interval from 303 to 285 °C, corresponding to onset–offset for NaNO3 solidification. Charge–self-discharge experiments on the pilot tank showed that the amount of thermal energy stored in this interval largely corresponds to the NaNO3 content of the microcapsules; the high temperature energy density of microcapsules is estimated in the range from 145 to 179 MJ/m3. Comparison between real tank experiments and FEM simulations demonstrated that DSC and TPS laboratory measurements on microcapsule thermal properties may reliably be used to design applications for thermal energy storage.

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