Papers by Keyword: Thermodynamic Property

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Authors: Gui Xiang Wang, Xue Dong Gong, He Ming Xiao
Abstract: The derivatives of HNS are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/ 6-31G* level. Their IR spectra are obtained and assigned by vibrational analysis. Compared with the experimental results, all the calculated IR data are found to be reliable. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic properties are evaluated, which are respectively linearly related with the number of methyl, azido and difluoramino groups as well as the temperature, obviously showing good group additivity.
Authors: Hotaruko Sugimura, Yasuyuki Kaneno, Takayuki Takasugi
Abstract: The site preference of ternary additions in Ni3X-type GCP compounds was determined from the direction of solubility lobe of the GCP phase on the experimentally reported ternary phase diagrams. In Ni3Nb (D0a), Co and Cu preferred the substitution for Ni-site, Ti, V and W the substitution for Nb-site, and Fe the substitution for both sites. In Ni3V (D022), Co preferred the substitution for Ni-site, Cr the substitution for both sites, and Ti the substitution for V-site. In Ni3Ti (D024), Fe, Co, Cu, and Si preferred the substitution for Ni-site, Nb, Mo and V the substitution for Ti-site. The thermodynamic model, which was based on the change in total bonding energy of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The bond energy of each nearest neighbor pair used in the thermodynamic calculation was derived from the heat of compound formation by Miedema’s formula. The agreement between the thermodynamic model and the result of the literature search was excellent. Both transition and B-subgroup elements have two possibilities, i.e., the case of substitution for Ni-site or the case for X-site, depending on the relative value of two interaction energies.
Authors: Hui Liu, Jun Tan, Ping Sun, You Qun Zhu, Jie Chen
Abstract: The fully optimized and vibrational analysis calculation of some silane compounds containing Si-Ph bonds were carried out at the B3LYP/6-31G* level, to obtain the thermodynamic parameters of the molecules in standard state 298.15K, 1.013 × 105 Pa. Based on the output file of the Gaussian 03 program, using the statistical thermodynamic program to calculate the molar constant pressure heat capacity (Cp, m)of phenyl substituted silane derivatives from 200K to 1800K, the correlation between the Cp, m and temperature (T, T-1 and T-2) was fitted with the least square method, and what was found was that the Cp, m of series of phenyl substituted silane derivatives had a very good correlation with T, T-1 and T-2.
Authors: Yang Chen, Mao You Chu, Li Jun Wang
Abstract: The structural, elastic and thermodynamic properties of the ternary layered nitrides Ti4AlN3 under the pressure effect have been calculated by using the full-potential linearized augmented plane-wave method within the generalized gradient approximation (GGA). The calculated properties such as cell parameters and bulk modulus, can found in good agreement with the experimental and other theoretical data. Using the quasi-harmonic Debye model in which the phonon vibration effects are considered, the thermodynamic properties such as thermal expansion coefficient, Debye temperature and specific heats in the whole pressure range from 0 to 50GPa and temperature range from 0 to 1600 K has been obtained.
Authors: Ben Hai Yu, Dong Chen
Abstract: the equilibrium lattice constants, elastic and thermodynamic properties of cubic CdTe are systemically investigated at high temperature using the plane-wave pseudopotential method as well as the quasi-harmonic Debye model. The bulk modulus of CdTe are calculated as a function of temperature up to 1000K, the relationship between bulk modulus B and pressure is also obtained. The results gained from this model will provide overall predictions accurately for the temperature and pressure dependence of various quantities such as the bulk modulus, the heat capacity and the thermal expansion coefficient. More over, the dependences between Debye temperature and temperature are also successfully obtained. Our results are compared with the experimental data and discussed in light of previous works.
Authors: Yue Zhang, Xue Gao, Jia Xiang Shang, Xiao Ping Han
Abstract: First-principles calculations have been widely used to describe the ground state properties of materials over almost 20 years. Recently, a great progress was made in the first-principle calculations. Thermodynamic properties can also be gotten by calculations of the phonon densities of states (phonon DOS) and phonon dispersions of materials, which show widely potential applications in material researches. In the present work, the energetics and bonding properties of interfaces between ZrO2 and Ni metal were given by first-principles calculations. The results show that alloy element impurities (Al, Cr and Y) influence remarkably the adhesion of the ceramic and metal. On the other hand, the phonon densities of states and phonon dispersions of ZrO2 were calculated with density functional perturbation theory. From the phonon DOS, the thermodynamic properties were derived and the phase transformation of ZrO2 was discussed. By this method, the thermodynamic properties of material can be gotten from atom and electron levels without any experiment data. It is a new approach to design and study the thermodynamic properties in new material system.
Authors: Ai Min Hao, Na Qi Wang
Abstract: We investigate the electronic, dynamic and thermodynamic properties of α-MnO2 using first-principles calculations based on density functional theory (DFT) with the GGA+U method. The results of electronic structures show that α-MnO2 is a semiconductor with a direct band gap of 1.4 eV at Γ point. The results of dynamic properties indicate that the structure of α-MnO2 is dynamically unstable at ground-state. Several important thermodynamic quantities, such as entropy, enthalpy and Gibbs free energy, et al each as a function of temperature were presented.
Authors: Ai Min Hao, Xiao Cui Yang, Li Xin Zhang, Qi Zhou Zhang
Abstract: An investigation on electronic, elastic and thermodynamic properties of VN under high pressure has been conducted using first-principles calculations based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. At elevated pressures VN is predicted to undergo a structural phase transition from the relatively open NaCl-type structure into the denser CsCl-type atomic arrangement. The predicted transition pressure is 189 GPa. The elastic constants, Debye temperature as a function of pressure and temperature of VN are presented.
Authors: David Fuks, Simon Dorfman, G. Ackland
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