The properties and electronic structure of Fe under pressures of 0-30GPa have been studied by flrst principles employing the density functional theory（DFT）,the ultra-soft pseudo-potentials（USPP）and the generalized gradient approximation（GGA）.The calculating results show that there is a structural transition from magnetic body-centered cubic（bcc）to nonmagnetic hexagonal-close-packed（hcp）structure for Fe around 11 GPa pressure.There is a pseudogap both in the density of states（DOS）for bcc and hcp Fe.The pseudogap of bcc Fe is deeper and wider than that of hcp Fe.The elastic modulus is obtained by Voigt-Reuss-Hill averaging scheme.The results indicate that the elastic properties of bcc Fe enhance with pressure except for elastic stiffness constant C11, shear modulus G and elastic modulus E at the transition pressure,while the elastic properties of hcp Fe increase linearly with pressure.Magnetic bcc Fe is ductile,and hcp Fe becomes ductile from brittle around 25 GPa.
The energy, electronic structure, and magnetic and mechanical properties of LaNi5 compound have been studied by the first-principles method based on the density functional theory. The results show that the calculated lattice parameters of LaNi5 compound are almost the same with the experimental ones, and the compound is easy to form and very stable. The bond between La and Nil atoms is an ionic bond, and electrostatic attraction effect exists between Ni atoms. The farther the distance between Ni atoms in the LaNi5 crystal cell is, the stronger the electrostatic attraction effect is. LaNi5 intermetallic compound is ductile and ferromagnetic. The calculated hardness value of LaNi5 compound is 7.04 GPa, and the calculated elastic properties are close to the experimental results.
