SiTi3机械合金化非晶化过程的研究

利用机械合金化方法得到了SiTi3非晶合金。经分析表明,SiTi3非晶合金是由于Si在Ti中的固溶量超过晶格稳定性限制,Ti的晶格发生“崩溃”而形成的,并对固溶量增加的原因进行了分析。     

Li-ion battery material under high pressure: amorphization and enhanced conductivity of Li4Ti5O12

Lithium titanium oxide (Li₄Ti₅O₁₂, LTO), a ‘zero-strain’ anode material for lithium-ion batteries, exhibits excellent cycling performance. However, its poor conductivity highly limits its applications. Here, the structural stability and conductivity of LTO were studied using in situ high-pressure measurements and first-principles calculations. LTO underwent a pressure-induced amorphization (PIA) at 26.9 GPa. The impedance spectroscopy revealed that the conductivity of LTO improved significantly after amorphization and that the conductivity of decompressed amorphous LTO increased by an order of magnitude compared with its starting phase. Furthermore, our calculations demonstrated that the different compressibility of the LiO₆ and TiO₆ octahedra in the structure was crucial for the PIA. The amorphous phase promotes Li⁺ diffusion and enhances its ionic conductivity by providing defects for ion migration. Our results not only provide an insight into the pressure depended structural properties of a spinel-like material, but also facilitate exploration of the interplay between PIA and conductivity.     

徐桦教授的计算机模拟工作评述

从三个方面评述了徐桦在分子动力学（简称MD）模拟方面所做的工作。一、移植了Anastasion和Fineham编著的大型MD程序到IBM4341和4361机上,对MD在国内推广起了促进和推动作用。二、模拟了熔盐及其互易系的性质,为一些困难实验现象和微观细节提供了合理解释。三、模拟了五个著名的压力非晶态系统。提供了实验上不能提供的微观细节,解释了某些重要实验事实。提出了不少新观点,为材料科学研究的进展做出了贡献。     

分子动力学模拟计算钙钛矿型CaSiO_3解压缩过程的红外振动谱

对钙钛矿型CaSiO3从高压下解压缩变成非晶态的过程进行了分子动力学模拟,模拟所得的压力-体积关系与实验值符合较好.利用不同压力下的平衡构型计算了红外振动频谱,给出了六张振动频谱图.这些频谱图的变化与结构的变化完全一致,也与配位数的变化一致.从谱图上,观察到了非晶态出现的特征和钙钛矿型结构崩溃的迹象.多非晶形性转变是在压力非晶化后才出现的,这是一个新论点.