Structural, elastic, electronic and chemical bonding properties of hydrides X2RuH6 (X = Mg and Ca): An ab initio study
O.Boudrifa1, A.Bouhemadou 2 .
was.boud@gmail,com
Laboratory of Developing New Materials and their Characterization. Department of Physics, Faculty of Science, University of Sétif 1, 19000 Sétif, Algeria
Abstract :
Several applications of hydrides have been found so far, e.g. switchable mirrors [1–2], energy storage [3,4], rechargeable batteries [4], etc. Using first-principals density functional calculations, we have studied the structural, electronic elastic and elastic properties of the complex hydrides Mg2RuH6, Ca2RuH6. The calculated structural properties; namely equilibrium lattice constants, internal free parameters, bulk modulus and its first-order pressure derivative, are in good agreement with the available results. The relative changes of the structural parameters versus hydrostatic pressure have been investigated. The elastic constants and their pressure dependence are predicted using the static finite strain technique and the polycrystalline isotropic elastic moduli, namely bulk modulus, shear modulus, Young’s modulus and Poisson’s coefficient, Lames coefficients, average sound velocity and Debye temperature are numerically estimated in the frame-work of the Voigt–Reuss–Hill approximations. The mechanical stability of the considered materials has been examined on the light of the pressure dependence of the elastic constants.The elastic anisotropy of the X2RuH6
has been studied using three different methods. The analysis of the site and momentum projected densities, charge transfer and charge densities show that bonding is of covalent-ionic nature. The band structures show that all studied materials are indirect energy band gap semiconductors.
Fig 1:Electronic band dispersion curves along the high symmetry directions in the Brillouin zone for the X2RuH6 (X = Mg, Ca) compounds.
-10 -5 0 5 10
Ca2RuH6
X W K
Γ L
W
Energy(ev)
-10 -5 0 5 10
Energy(ev)
Mg2RuH6
W K
Γ X L
W
0 2 4 6 8 10
V14 C1
V2
V13 V12 C16
C15 C14 C13 C12
C11 V11
Mg2RuH6
V1
0.0 0.1 0.3 0.6 0.9
Mg s Mg p
0 2 4
6 Ru s
Ru p Ru d
-40 -30 -20 -10 0 10
0.0 0.1 0.2 0.3 0.4 T DOS (état/ev/maille)
P DOS (état/ev/maille)
Energy(ev) H s
0 2 4 6 8 10
12 V
4 V3
C1
V14V13V12 C16C15
C14 C13 C12
C11
Ca2RuH6
T DOS (état/ev/maille) V11
V1
0.0 1.01.5 2.02.5
V2
Ca S Ca p Ca d
0 24
68 Ru S
Ru p Ru d
-40 -30 -20 -10 0 10
0.0 0.1 0.2 0.3 0.4 P DOS (état/ev/maille)
Energy(ev)
H S
Fig 2: Total (TDOS) and partial (PDOS) densities of states diagrams for the X2RuH6 (X = Mg, Ca) compounds.
Fig 3: Charge density distribution maps in (110) plane for the X2RuH6 (X = Mg, Ca) compounds.
Keywords: Structural, elastic, electronic, chemical bonding ab initio c a l c u l a t i o n s , Electronic band, densities of states ,Charge density.
References
[1] ] J.N. Huiberts, R. Griessen, J.H. Rector et al., Nature 380 (1996) p.231.
[2] J.W.J. Kerssemakers, S.J. van der Molen, N.J. Koeman et al., Nature 406 (2000) p.489.
[3] P. Chen, Z.T. Xiong, J.Z. Luo et al., Nature 420 (2002) p.302.
[4] L. Schlapbach and A. Zu¨ ttel, Nature 414 (2001) p.353.
