title: New stable Re-B phases for ultra-hard materials.
abstract: As a distinct class of ultra-hard materials, transition metal borides are found to have superior mechanical properties that challenge the traditional materials. In this work, we explored new stable structures for rhenium borides with different stoichiometries using genetic algorithm in combination with first-principles calculations. Based on theoretical calculations, ReB in a P-3m1 structure is found to be stable against decomposition reactions below 10 GPa and ReB3 in a P-6m2 structure is stable above 22 GPa. Two new phases of Re(2)B are predicted to be thermodynamically stable at pressures higher than 55 GPa and 80 GPa respectively. We also show that a C2/m structure discovered for ReB(4) has energy lower than that of the R-3m structure reported earlier (Wang et al 2013 J. Alloys Compd. 573 20). Elastic and vibrational properties from first-principles calculations indicate that the low-energy structures obtained in our search are mechanically and dynamically stable and are promising targets as new ultra-hard materials.
authors.affiliation: Ames Laboratory, US DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
authors.forename: Manh Cuong
authors.initials: MC
authors.lastname: Nguyen
authors.forename: Cai-Zhuang
authors.initials: CZ
authors.lastname: Wang
authors.forename: Kai-Ming
authors.initials: KM
authors.lastname: Ho