First Principle Calculations For The Lattice And Thermodynamics Of Copper、Iron

Based on the first-principles, employing the density functional theory and it’s perturbation theory, and the methods of generalized gradient approximation (GGA) and TM pseudo-potential. This thesis studies the phonon spectrum and density of states for the transition metal Cu, and its thermodynamic functions such as entropy, Gruneisen parameter and in the condition of298.15K and compares it with that of the experimental data as well. By analyzing the relationship between the energy optimization path and lattice vibration of Cu, this paper presents the phase transition mechanism as per the nature of solid-liquid phase and introduces the static method to derive the melting temperature of transition metals. Compared with that of the experiment, the melting temperature pressure curve in this paper is more favorable than the result of molecular dynamic simulation.By employing the first-principles of generalized gradient approximation (GGA) and the modified TM pseudo-potential this thesis furthermore analyzes the electronic band structure and density of states for the transition metal Fe in different crystalline structures(8-bcc、γ-fcc、α-bcc、ε-hcp), and its thermodynamic functions such as heat capacity and entropy in the condition of298.15K and compares it with that of the experimental data as well.(1) The energy curves of this polycrystalline phase Fe in the condition of y-fcc crystalline phase is calculated. The relationship between the melting temperature and pressure (0-200GPa) of y-Fe is derived by static method, which fits well compared with that of the diamond anvil cell.(2) By analyzing the relationship between the energy optimization path and lattice vibration of Fe in the condition of8-bcc phase, this paper proposes the phase transition mechanism for the nature of solid-liquid phase. The calculation indicates that the impact of volume to the total energy system should be taken into consideration when the temperature and pressure of δ-Fe is1~5.2GPa.(3) In the calculation of the energy curves of polycrystalline phase Fe, the impact of the inner shell electron on the outermost shell3s23P6should also be taken into consideration.