非弹性中子散射：确定平衡同位素分馏因子的新方法。金刚石heat capacity及β因子的尺寸效应
Inelastic neutron scattering: A novel approach towards determination of equilibrium isotopic fractionation factors. Size effects on heat capacity and beta-factor of diamond
摘要：
提出了一种基于非弹性中子散射（INS）测定物质平衡同位素性质的新实验方法。我们提出的数学形式主义，允许计算的β因子的单元素固体的基础上INS导出的声子态密度（PDOS）。从非弹性中子散射实验确定了不同尺寸的纳米金刚石和宏观金刚石的PDOS数据。这允许测定热容，并首次测定金刚石纳米颗粒的\b{eta}因子。我们证明了相当大的尺寸依赖性的增加的热容量和减少的β因子的纳米金刚石相对于散装金刚石。表面杂质/相位和声子限制的尺寸效应的贡献进行了评估。简要讨论了金刚石纳米粒子在自然界中的应用。
英文摘要：
A new experimental method of determination of equilibrium isotopic properties of substances based on Inelastic Neutron Scattering (INS) is proposed. We present mathematical formalism allowing calculation of beta-factor of single-element solids based on INS-derived Phonon Density of States (PDOS). PDOS data for nanodiamonds of widely different sizes and of macroscopic diamond were determined from Inelastic Neutron Scattering experiment. This allowed determination of heat capacities and, for the first time, \b{eta}-factors for the diamond nanoparticles. We demonstrate considerable size-dependent increase of the heat capacities and decrease of the beta-factors for nanodiamonds relative to bulk diamond. Contributions of surface impurities/phases and phonon confinement to the size effects are evaluated. Applications to formation of diamond nanoparticles in nature are briefly discussed.
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