Model creation and electronic structure calculation of amorphous hydrogenated boron carbide: a classical/ab initio hybrid approach

Abstract

Amorphous hydrogenated boron carbide (a-BC:H), grown by plasma enhanced chemical vapor deposition of orthocarborane precursors, is an amorphous molecular solid with strong short range order, no long range order, and unknown medium range order. Determination of the structure of a-BC:H is an essential prerequisite for obtaining predictive control over its fabrication. The aim of this work is to establish an approach for modeling molecular amorphous solids, as well as to create and analyze geometry optimized models of a-BC:H that are consistent with experimental data from the literature. The modeling process combines classical molecular dynamics and ab initio electronic structure methods. Further, general trends were established between the composition and electronic structure properties. The total density of states shows semi-metal behavior with an approach toward semi-conducting behavior with reduced H content. A similar but weaker trend was apparent for B content. Also, the percent contents of both hydrogen and boron were found to be inversely proportional to the dielectric constant. These electronic structure results are in line with other experimental results reported in the literature. The proposed modeling method was found to be suitable and effective for a-BC:H and its applicability to other members of this family of solids is also expected.