钛纳米线力学、热学和电子性质的结构与尺寸依赖性

为了研究金属纳米物理性质与结构和尺寸之间的关系,我们选择不同结构和生长序列的几个典型的超细Ti纳米线,即四边形、五边形和六边形序列,以及六边形序列的两个较大体系,以分别考察结构和尺寸效应.我们计算了Ti纳米线的角关联函数和振动谱,电子态密度用平面波赝势的密度泛函电子结构自洽场计算.采用分子动力学方法研究Ti纳米线的热力学融化行为.结果表明,Ti纳米线的振动性质和电子性质表现出渐进的尺寸演化和明显的结构关联;较小的纳米线的电子态密度是类似分子的离散谱,而当线的直径大于1*!nm时便表现为类似体材料的电子结构.Ti纳米线的融化行为既不同于团簇也不同样块体材料,表现出明显的结构和尺寸依赖性.对较大尺寸的纳米线,我们观察到从螺旋多壳的圆柱体到类似块体的结构相变.

Structural and Size Effects of Mechanical, Thermodynamic,and Electronic Properties in Titanium Nanowires

Some typical structures of titanium nanowires, i.e. four strands helical, centered pentagonal, hexagonal and the thicker hexagonal structures are chosen to study the structural and size effects of ultrathin nanowires. The angular correlation functions and vibrational properties are discussed. We have further calculated the electronic structures of the titanium nanowire by using density functional electronic structure self consistent field (SCF) calculations with the plane wave pseudopotential method. The vibrational and electronic properties of titanium nanowire depend on the structure and size. Bulk like continuous electronic band are formed in the Ti wires thicker than 1 nm. We have studied the thermal stability of the titanium nanowires by using molecular dynamical simulation (MD) starting from the optimized structures. The structural transformation from the helical multi shell cylindrical to the bulk like for the thicker nanowire is observed which takes place in the melting process. The thermal properties of titanium nanowires are significantly dependent on the structure and size of the nanowires.