摘要
液体硒是典型的半导体,在高温高压下临界点邻近发生半导体-金属-绝缘体(SC-M-I)转变。为了研究高温高压下流体硒在SC-M-I转变过程中结构的变化,利用SPring-8的同步辐射光对高温高压下流体硒进行了能量色散X射线衍射测量和小角X射线散射测量。测量范围包括液态区、超临界区和稠密气态区域。在衍射实验中,我们获得了精确的结构因子S(k)和偶分布函数g(r)。结果证实了在金属液体区域中流体硒仍保持两配位的链结构和共价键轻微地收缩,还发现随着流体硒的金属特性的增强g(r)的第一极小值发生了显著的增加,即Se链的链间相互作用增强。小角散射结果表明在临界密度邻近,密度的涨落显著,相干长度存在极大值。这些结果表明Se链的共价键的特性和 Se链间的相互作用是理解流体硒中的 SC-M-I 转变的机制的关键。
Liquid Se, well-known as a typical semiconductor, undergoes semiconductor-to-metal (SC-M) transition at high temperature and pressure in the vicinity of the critical point. To understand such peculiar electronic and atomic structures of liquid Se, we have performed energy-dispersive X-ray diffraction measurements (EDXD) and small angle X-ray scattering (SAXS) using synchrotron radiation at SPring-8 for fluid Se, including liquid and dense vapour regions. The obtained structure factors, S(k), and the pair distribution functions, g(r), are with good accuracy by using a new high pressure vessel with 7 scattering windows. Besides confirming the preservation of twofold coordinated structure and the contraction of the nearest coordination distance in the metallic fluid region, it was found that the value of the first minimum in the g(r) increases obviously with increasing metallic properties, indicating the interaction enhancement of interchain in fluid Se. The SAXS experiment shows that the density fluctuation plays an important role in the formation of Se chain or Se dimer.
出处
《核技术》
CAS
CSCD
北大核心
2003年第4期249-253,共5页
Nuclear Techniques
关键词
同步辐射
高温高压流体
结构分析
X射线衍射
X射线散射
流体硒
半导体
Synchrotron radiation, High-temperature high-pressure fluid, Structural analysis, X-ray diffraction, X-ray scattering
