Al_(89)La_6Ni_5非晶合金的第一性原理分子动力学模拟

Ab initio molecular dynamics simulation of Al_(89)La_6Ni_5 metallic glass

采用第一性原理分子动力学(AIMD)方法模拟Al89La6Ni5合金的退火过程,结合双体相关函数和配位多面体(团簇)分布分析了体系短程有序结构随温度的演化.结构分析表明,非晶态Al89La6Ni5原子短程有序结构近似密堆排列;在非晶形成过程中,Al原子周围短程有序结构几乎没有发生变化,而La和Ni原子周围环境发生明显改变,由此推测,La原子的加入改变了Ni原子周围的短程有序结构,因而增加了Al-La-Ni体系的非晶形成能力;Al原子和Ni原子间存在Al-Ni共价键作用,电子态密度的计算说明,费米面附近Al-p和Ni-d之间电子的相互作用是Al-Ni原子间形成局域共价键的原因.

Ab initio molecular dynamics simulation of Al89La6Ni5 alloy were performed at descending temperatures to discuss the evolution of short- range order( SRO) with temperature,the pair correlation functions,coordination polyhedron( clusters) have been analyzed. This work suggests the SRO of atoms is near densely packed in the glassy state. With temperature decreasing to glassy state,the SRO of Al atoms changes slightly,while the environment around La and Al atoms has obviously variation. Thus it can be inferred,by La addition,the environments of Ni atoms changed,resulting in improved glass forming ability for the Al- La- Ni alloys. The result provides strong evidence for the existence of Al – Ni covalent bonds,analysis of electronic structures further revealed that the interaction between Al- p and Ni- d electrons near Fermi level is responsible for the enhanced Al- Ni bonding.