title: Structural prediction of ultrahard semi-titanium boride (Ti2B) using the frozen-phonon method.
abstract: The dynamical stability, crystal structure, and mechanical properties of semi-titanium boride (Ti2B) are extensively studied using the pseudopotential plane-wave method within first-principles calculations. Soft transverse acoustic phonon modes are identified in the material, which has been assumed for a long time to have an Al2Cu-type structure with a I4/mcm space group. Using the frozen-phonon method, a tetragonal I4/m structure is uncovered to be energetically more stable and have similar diffraction patterns compared to the previously assumed Al2Cu-type structure. Phonon dispersion and elastic constant calculations reveal the dynamical and mechanical stability of the I4/m structure of Ti2B at ambient pressure. The calculated high elastic constants, modulus, and ideal strength show that Ti2B possesses outstanding mechanical properties.
authors.affiliation: Laboratory of Clean Energy Technology, Changchun University of Science and Technology, Changchun 130022, China. Zhoudan777@aliyun.com.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhou
authors.affiliation: Department of Physics, College of Science, Yanbian University, Yanji 133000, China. yhliu@ybu.edu.cn.
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Laboratory of Clean Energy Technology, Changchun University of Science and Technology, Changchun 130022, China. Zhoudan777@aliyun.com.
authors.forename: Bingjun
authors.initials: B
authors.lastname: Shen
authors.affiliation: Laboratory of Clean Energy Technology, Changchun University of Science and Technology, Changchun 130022, China. Zhoudan777@aliyun.com.
authors.forename: Xinle
authors.initials: X
authors.lastname: Zhao
authors.affiliation: School of Science, Changchun University of Science and Technology, Changchun 130022, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Laboratory of Clean Energy Technology, Changchun University of Science and Technology, Changchun 130022, China. Zhoudan777@aliyun.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Tian