Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$

Details Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$ Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$

2001-08-17

arxiv.org/abs/cond-mat/0108278v1

Physics

Condensed Matter

Materials Science

14 pages, 9 figures

Scientific paper

10.1103/PhysRevB.65.075101

We present the results of theoretical investigation on the electronic structure, bonding nature and ground state properties of Th$_2$Al and Th$_2$AlH$_4$ using generalized-gradient-corrected first-principles full-potential density-functional calculations. Th$_2$AlH$_4$ has been reported to violate the "2 \AA rule" of H-H separation in hydrides. From our total energy as well as force-minimization calculations, we found a shortest H-H separation of 1.95 {\AA} in accordance with recent high resolution powder neutron diffraction experiments. When the Th$_2$Al matrix is hydrogenated, the volume expansion is highly anisotropic, which is quite opposite to other hydrides having the same crystal structure. The bonding nature of these materials are analyzed from the density of states, crystal-orbital Hamiltonian population and valence-charge-density analyses. Our calculation predicts different nature of bonding for the H atoms along $a$ and $c$. The strongest bonding in Th$_2$AlH$_4$ is between Th and H along $c$ which form dumb-bell shaped H-Th-H subunits. Due to this strong covalent interaction there is very small amount of electrons present between H atoms along $c$ which makes repulsive interaction between the H atoms smaller and this is the precise reason why the 2 {\AA} rule is violated. The large difference in the interatomic distances between the interstitial region where one can accommodate H in the $ac$ and $ab$ planes along with the strong covalent interaction between Th and H are the main reasons for highly anisotropic volume expansion on hydrogenation of Th$_2$Al.

Affiliated with

Also associated with

No associations

Rating

Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$ does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic structure, phase stability and chemical bonding in Th$_2$Al and Th$_2$AlH$_4$ will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-544086