M2M'AlB4 (M =Mn, Fe, Co, M'=Cr, Mo, W): Theoretical predicted ordered MAB phases with Cr3AlB4 crystal structure

• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2019,（7）
• 页码范围: 1432-1438
• 页数: 7页
• 语种: 英文

摘要

The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties,which is similar to MAX phases.Recently,ordered quaternary MAX phases have been discovered,which enriches the family of MAX phases,and opens a new window to tailor the properties of MAX phases and to develop new MXenes.In the present work,we explored possible ordered quaternary MAB phases with Cr3AlB4 structure (space group:Pmmm) by first-principles calculations.The predictions show that M2M'AlB4 phases with M =Mn,Fe,Co and M'=Ct,Mo,W exhibit strong tendency of ordering,where M locates at 2t site (0.5,0.5,z2t) and M'locates at 1g site (0,0.5,0.5).The main driving force of ordering may be the differences in bonding strengths between Al and M elements.Analyses on chemical bonds reveal that bonding strengths increase following the order:Al-Mn ＜ Al-Fe ＜ Al-Co,which is consistent with the prediction that ordering tendency increases when M changes from Mn to Co,as derived from enthalpy differences.The ordered M2M'AlB4 phases with M =Mn or Fe are predicted ferromagnetic and ordered M2M'AlB4 phases display lower shear resistance and possibly better ductility in comparison to Cr3AlB4.