Amorphous boron suboxide

Abstract

We study the atomic structure and the electronic and mechanical properties of amorphous boron suboxide (B 6 O) using an ab initio molecular dynamic technique. The amorphous network is attained from the rapid solidification of the melt and found to consist of boron and oxygen-rich regions. In the boron-rich regions, boron atoms form mostly perfect or imperfect pentagonal pyramid-like configurations that normally yield the construction of ideal and incomplete B 12 molecules in the model. In addition to the B 12 molecules, we also observe the development of a pentagonal bipyramid (B 7 ) molecule in the noncrystalline structure. In the oxygen-rich regions, on the other hand, boron and oxygen atoms form threefold and twofold coordinated motifs, respectively. The boron-rich and oxygen-rich regions indeed represent structurally the characteristic of amorphous boron and boron trioxide (B 2 O 3 ). The amorphous phase possesses a small band gap energy with respect to the crystal. On the bases of the localization of the tail states, we suggest that the p-type doping might be more convenient than the n-type doping in amorphous B 6 O. Bulk modulus and Vickers hardness of the noncrystalline configuration is estimated are be 106 and 13-18 GPa, respectively, which are noticeably less than those of the crystalline structure. Such a noticeable decrease in the mechanical properties is attributed to the presence of open structured B 2 O 3 glassy domains in the amorphous model. K E Y W O R D Samorphous, boron suboxide, hardness

Growth of Millimeter Size B6O Single Crystals in a B-H3BO3 System at High Pressure and High Temperature

“…The B–s state makes a certain contribution to the conduction band, and the O–p state makes some contribution to the valence. These findings are consistent with previous simulations. − …”