OsH : An ab initio study Structural, elastic, electronic and chemical bonding properties of the semi-conductor matérials Ba

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Structural, elastic, electronic and chemical bonding properties of the semi- conductor matérials Ba

2

OsH

6

: An ab initio study

O.Boudrifa ^a, A.Bouhemadou^b

.

a, b Department of Physics, Laboratory of Developing New Materials and their Characterization. Faculty of Science, University of Sétif 1, 19000 Sétif, Algeria.

was.boud@gmail,com ABSTRACT

:

Several applications of hydrides have been found so far. During the last decade, applications such as hydrogen storage/economy [1,2], rechargeable batteries [2], etc., have been the subject of intensive research efforts. After the discovery of the switchable optical properties of yttrium and lanthanum hydride films [3], hydrides have found another application as smart windows [3–4]. For the above listed specific applications of hydrides fast kinetics of hydrogenation/dehydrogenation processes, low temperature at which the hydrogenation/dehydrogenation occurs, large hydrogen content, low total weight and powder form of hydrides are extremely important. However, hydrides with large total weight, low concentration of hydrogen atoms and high temperature for activation of hydrogenation/dehydrogenation processes have received little or no attention. Recently, this class of hydrides has been suggested as a source of important applications in semiconductor electronics, such as transparent conducting materials [5] and semiconductor p–n junctions [6].

Using first-principals density functional calculations, we have studied the structural, electronic, elastic and chemical bonding properties of the complex hydrides Ba2OsH6.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 Sr2OsH6 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.

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Fig 1: Electronic band dispersion curves along the high symmetry directions in the Brillouin zone and Total (TDOS) and partial (PDOS) densities of states diagrams for the Sr

2

OsH

6

compounds.

Fig 2: Charge density distribution maps in (110) plane for the Ba

2

OsH

6

compound.

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] P. Chen, Z.T. Xiong, J.Z. Luo, J.Y. Lin and K.L. Tan, Nature 420 (2002) p.302.

[2] L. Schlapbach and A. Zu¨ ttel, Nature 414 (2001) p.353.

[3] J.N. Huiberts, R. Griessen, J.H. Rector, R.J. Wijngaarden, J.P. Dekker, D.G.d. Groot and N.J. Koeman, Nature 380 (1996) p.231.

[4] J.L.M. van Mechelen, B. Noheda, W. Lohstroh, R.J. Westerwaal, J.H. Rector, B. Dam and R. Griessen, Appl.

Phys. Lett. 84 (2004) p.3651.

[5] S.Z. Karazhanov, P. Ravindran, P. Vajeeston and A.G. Ulyashin, Phys. Status Solidi (a) 204 (2007) p.3538.

[6] S.Z. Karazhanov, A.G. Ulyashin, P. Ravindran and P. Vajeeston, Eur. Phys. Lett. 82 (2008) p.17006.

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Ba2OsH6