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Thermodynamics and elastic properties of Ta from first-principles calculations

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Chinese Physics B 2012年第12期21卷 412-419页

作者：李强黄多辉曹启龙王藩侯蔡灵仓张修路经福谦 Computational Physics Key Laboratory of Sichuan Province Yibin University Key Laboratory of National Defense Science and Technology for Shock Wave and Detonation Physics and the Science

Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of Ta, including phonon density of states （DOS）, equation of state, linear thermal expansion coefficient, entropy, enthalpy, heat capacity, elastic constants, bulk modulus, shear modulus, Young＇s modulus, microhardness, and sound velocity, are studied using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon DOS and the debye model. The thermal electronic contribution to Helmholtz free energy is estimated from the integration over the electronic DOS. By comparing the experimental results with the calculation results from the first-principles and the debye model, it is found that the thermodynamic properties of Ta are depicted well by the first-principles. The elastic properties of Ta from the first-principles are consistent with the available experimental data.

关键词： first-principles Ta thermodynamics debye model elastic properties

Thermodynamic properties of 3C-SiC

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Chinese Physics B 2013年第10期22卷 429-435页

作者： B.Y.Thakore S.G.Khambholja A.Y.Vahora N.K.Bhatt A.R.Jani Department of Physics Sardar Patel UniversityVallabh Vidyanagar388120GujaratIndia Indus University Ahmedabad 380001GujaratIndia

In the present paper, we report on the results of various thermodynamic properties of 3C-SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as im- plemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic debye model. The calculated thermody- namic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.

关键词： phase transition phonon dispersion curve debye model thermodynamic property

Study of the properties of non-gas dielectric capacitors in porous media

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Petroleum Science 2015年第1期12卷 104-113页

作者： Hong-Qi Liu Yan Jun You-Ming Deng State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Centrica Energy (E&P) Upstream Kings Close

The size of pores and throats is at the nano- meter scale in tight oil and shale gas zones, and the resistivity of these reservoirs is very high, so the reservoirs show more dielectric properties than conductivity proper- ties. The conductive and dielectric characteristics of a parallel plate capacitor full of fresh water, NaCl solutions, and solid dielectrics, for example, sands are investigated in this paper, and the capacitance data of the non-gas capacitor are measured at different salinities and frequencies by a spectrum analyzer. The experimental results illustrate that the capacitance of this kind of capacitor is directly pro- portional to the salinity of the solutions and inversely proportional to the measuring frequency, the same as a vacuum parallel plate capacitor. The remarkable phenom- enon, however, is that the capacitance is inversely pro- portional to the square of the distance between two plates. The specific characteristic of this capacitor is different from the conventional parallel plate capacitor. In order to explain this phenomenon, the paper proposed a new concept, named ＂single micro ion capacitor＂, and established a novel model to describe the characteristics of this particular capacitor. Based on this new model, the theoretical capacitance value of the single micro ion capacitor is calculated, and its polarization and relaxation mechanisms are analyzed.

关键词： NaCl solution debye model Single micro ion capacitor Dielectrics Micro capacitivity

First-principles calculation of structural and thermodynamic properties of titanium boride

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Journal of Central South University 2011年第6期18卷 1773-1779页

作者：李燕峰徐慧夏庆林刘小良 School of Physical Science and Technology Central South University School of Materials Science and Engineering Central South University

The equilibrium lattice parameters, electronic structure, bulk modulus, debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.

关键词： electronic structure debye model thermodynamic properties density functional theory titanium boride

Large Scale Analysis of Complex Permittivity of Breast Cancer in Microwave Band

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Advances in Breast Cancer Research 2020年第4期9卷 101-109页

作者： Yoshihiko Kuwahara Akira Nozaki Kimihito Fujii Department of Electric and Electronical Engineering Faculty of Engineering Shizuoka University Hamamatsu Japan Division of Breast and Endocrine Surgery Department of Surgery Aichi Medical University Nagakute Japan

To obtain some prior knowledge of breast cancer detection by microwave imaging, we have measured and analyzed the complex permittivity of tissues extracted from over 140 breast cancer surgeries. The relative permittivity and conductivity of tumor at 1.6 GHz were 17.5% and 16.2% higher than those of mammary gland tissue, respectively. In invasive ductal carcinoma of scirrhous type, 8 out of 64 had higher relative permittivity and conductivity of mammary gland than those of tumor. However, when evaluated by the debye parameter considering the frequency dependence of the tissue, it is rare that ε∞ and Δε of cancer are simultaneously lower than those of mammary gland. The relative permittivity and conductivity of fibroadenoma are almost the same as those of mammary glands. The relative permittivity and conductivity of each tissue showed strong linearity. Microwave imaging requires accurate reconstruction of ε∞ and Δε to distinguish cancer from normal tissue.

关键词： Breast Cancer Detection Microwave Imaging Complex Permittivity debye model