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- Title
Theoretical studies of the elastic and thermodynamic properties of BCC metals with temperature.
- Authors
LIU Ruiping; XIAO Lijun; HAO Luyao; LI Xiuyan; YANG Zhi; XU Lichun
- Abstract
Based on the density functional theory, the elastic and thermodynamic properties of BCC metals have been calculated by using the first-principles method. Firstly, the lattice constants of BCC metals are optimized by using two different exchange correlation functions, general gradient approximate (GGA) and local density approximation (LDA) at 0 K. Compared with the results from LDA, the results from the GGA-PAW are more closer to the experimental results. Therefore, it is important to choose appropriate exchange correlation function. Secondly, based on the density functional theory (DFT) and density-functional perturbation theory (DFPT), calculation shows the elastic constant decreases with the increase of temperature. The temperature-dependence elastic constants indicate that BCC phase Ta, Fe, W, Mo are mechanically stable. In addition, the ratio of bulk modulus to shear modulus (B/G) has been studied. It is indicated that the four metals all show the toughness at the temperature of 0-1 500 K. Last, the thermodynamic properties including the thermal expansion coefficients, heat capacity at constant volume CV, the isobaric heat capacity CP are predicted. It is found that heat capacity at constant volume follows T³ theorem in low temperature (0-300 K), and follows the equipartition theorem in high temperature (1 000-1 500 K), which can prove the rationality of the calculation method.
- Publication
China Sciencepaper, 2018, Vol 13, Issue 5, p511
- ISSN
2095-2783
- Publication type
Article