Structural distortion and band gap opening of hard MnB₄ in comparison with CrB₄ and FeB₄

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• 作者：Meng Yang¹ ; ^a ; Yachun Wang¹ ; ^a ; Jinlei Yao^b ; Zhiping Li^c ; Jian Zhang^d ; Lailei Wu^a ; Hui Li^a ; Jingwu Zhang^a ; ^{zjw@ysu.edu.cn" class="auth_mail} ; Huiyang Gou^a ; ^{huiyang.gou@gmail.com" class="auth_mail}
• 关键词：MnB4 ; Structural distortion ; Band gap opening ; High hardness ; First-principles calculation
• 刊名：Journal of Solid State Chemistry
• 出版年：May, 2014
• 年：2014
• 卷：213
• 期：Complete
• 页码：52-56
• 全文大小：2469 K

文摘

MnB₄ was newly synthesized to crystallize in a monoclinic P2₁/c structure, different from previous experimental and theoretical reports. Here, based on first-principles calculations, we perform a comparative study of geometric and energetic features, mechanical behaviors, electronic property and chemical bonding of the experimentally identified monoclinic MnB₄, as well as orthorhombic CrB₄ and FeB₄. The results demonstrate that the presence of distorted rhomboidal-B₄ units and one-dimensional Mn chains in the monoclinic MnB₄ breaks the structural symmetry and lowers the total energy in comparison to the orthorhombic phase. The opening of band gap in MnB₄ is induced by Peierls-paired Mn atoms, differing from the metallic behaviors of recently studied tetraborides. Specifically, the preservations of covalent bonding in distorted boron-rhomboids in MnB₄ explain the relatively higher incompressibility and hardness.