A theorical study of electronic and structural properties of MgH2 containing vacancies and substituent atoms

C. R. LUNA; E. GERMÁN; C. MACCHI; A. JUAN; A. SOMOZA

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2012 vol. 556 p. 188 - 197

0925-8388

The electronic and structural properties of MgH2 systems containing vacancies and Zr orNb as dopants were studied using self-consistent calculations. The density of states (DOS)were computed using the Vienna Ab-initio Simulation Package (VASP) and the orbitaloverlap population weighted DOS with the Amsterdam Density Functional program. Themetal-metal and metal-hydrogen bonds in the perfect hydride and this material containing aMg, a H or a mixed Mg-H vacancy complex were analyzed. The same calculations werealso performed in the magnesium hydride with a Nb or a Zr atom as a substitutionalimpurity and on these systems containing the above mentioned vacancies. Simultaneously,the influence of vacancies in the hydride was studied through the calculation of the positronlifetimes and the electron-positron momentum distributions in the previously referredmaterials. Secondly, information on the influence of vacancies on the electron momentumdensity of the MgH2(-Nb,-Zr) systems was additionally obtained through the calculation ofthe electron-positron momentum distributions. The results obtained indicate that in the purehydride the presence of vacancies and impurities notable diminishes the force in the atomicbonds. The stability decrease of the bonds was correlated with changes in the positron wavefunction in the same sites of the structures. Moreover, it was found that these changes in thepositron wave function are in good agreement with the decrease of the positron lifetimes