https://doi.org/10.1140/epjb/e2015-60749-1
Regular Article
Ab initio study of intrinsic defects and diffusion behaviors in solid molecular hydrogens
1 School of Physical Electronics,
University of Electronic Science and Technology of China, Chengdu
610054, P.R.
China
2 School of Science, Huaihai Institute
of Technology, Lianyungang
222005, P.R.
China
3 Institute of Nuclear Physics and
Chemistry, China Academy of Engineering Physics, Mianyang
621900, P.R.
China
4 Department of Materials Science and
Engineering, University of North Texas, Denton, TX
76203,
USA
a
e-mail: yanglildk@uestc.edu.cn
Received:
17
September
2015
Published online:
14
December
2015
The behaviors of intrinsic defects in solid molecular hydrogens (H2) were investigated using ab initio calculations based on density functional theory. The results show that the formation energy of a vacancy is dependent on molecule orientation in disordered hexagonal close-packed (hcp) H2 crystals, but independent of molecular orientation in face-centered cubic-Pa3 H2. Furthermore, H2 molecules generally prefer to occupy the basal octahedral sites in hcp and octahedral sites in Pa3 structures. The formation energies of an interstitial H2 depend sensitively on the volume of interstitial sites, and also on near spatial distributions of molecular axes of a H2 in hcp H2 crystals. The strong force field introduced by an interstitial H2 might induce the rotation of molecular axes and reduce the formation energy of the interstitial H2. The migration barrier energy of a vacancy in Pa3 is larger than the average in hcp structures. However, the H2 molecules prefer to jump though vacancies in the two structures of solid H2 than the interstitial migrations.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2015
