First-principles prediction on the high-pressure structures of transition metal diborides (TMB2, TM = Sc, Ti, Y, Zr)

Meiguang Zhang; Hui Wang; Hongbo Wang; Xinxin Zhang; Toshiaki Iitaka; Yanming Ma

doi:10.1021/ic100214v

First-principles prediction on the high-pressure structures of transition metal diborides (TMB2, TM = Sc, Ti, Y, Zr)

Inorg Chem. 2010 Aug 2;49(15):6859-64. doi: 10.1021/ic100214v.

Authors

Meiguang Zhang¹, Hui Wang, Hongbo Wang, Xinxin Zhang, Toshiaki Iitaka, Yanming Ma

Affiliation

¹ National Laboratory of Superhard Materials, Jilin University, Changchun 130012, People's Republic of China.

PMID: 20578702
DOI: 10.1021/ic100214v

Abstract

We have extensively explored the high-pressure structures of transition-metal diborides (TMB(2), TM = Sc, Ti, Y, and Zr) stabilized with the AlB(2)-type structure at ambient pressure by using first-principles structural prediction. We find two novel high-pressure structures: (i) a monoclinic structure (C2/m, Z = 4) for ScB(2) and YB(2) stable above 208 and 163 GPa, respectively; and (ii) a tetragonal alpha-ThSi(2)-type phase (I4(1)/amd, Z = 4) for TiB(2) stable above 215 GPa. Our calculations show that the electron transfer from transition-metals TM to B under pressure might be the main cause for the structural phase transitions. Further phonon and hardness calculations suggest that alpha-ThSi(2) phase of TiB(2) is quenchable to ambient pressure and possesses excellent mechanical property with a Vickers hardness of 29.8 GPa. Interestingly, ZrB(2) is quite stable and persists on the ambient-pressure AlB(2)-type structure up to at least 300 GPa. We attribute the strong covalent hybridization between the transition-metal Zr and B to this ultrastability.