First-principles investigation of Mg2CoH5 complex hydride
(1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University,
Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Abstract: Within the framework of density functional theory, crystal structure parameters, physical properties, electronic structures and thermal stability of Mg2CoH5 complex hydride are comprehensively investigated. The optimized structural parameters including lattice constants, atomic positions and bond lengths are well close to the experimental data determined from X-ray and neutron powder diffraction. A detailed study on the energy band, density of states (DOS) and charge density distribution shows the orbital hybridization and bonding characteristics of the complex hydride. It is found that Mg2CoH5 is a semiconductor with a pseudo-gap of about 1.638 1 eV, and there is a mixed ionic-covalent bonding between Co and H in CoH5 complexes embedded in the matrix Mg2+ cations. The calculated formation enthalpy of Mg2CoH5 is in good agreement with the experimentally determined value.
Key words: Mg2CoH5; density functional theory; electronic structure; formation enthalpy