非晶硅和石英玻璃的静态结构因子
The static structure factor of amorphous silicon and vitreous silica
摘要：
液体处于热平衡并且具有非零静态结构因子S（Q->0）= [<N^2>-<N>^2]/<N>= rho*k_B*T*Chi_T其中rho是数密度，T是温度，Q是散射矢量，并且Chi_T是等温压缩性。这个结果的第一部分涉及N（或密度）的涨落，这是一个纯粹的几何结果，不涉及任何关于热平衡或遍历性的假设，因此所有材料都服从。从非晶硅的大型计算机模型，局部数涨落外推得到S（0）= 0.035+/-0.001。在仅使用硅原子并重新缩放距离的玻璃质二氧化硅的大模型上进行的相同计算给出S（0）= 0.039+/-0.001，这表明该数值结果对于所有无定形四面体网络是稳健且相似的。对于玻璃石英，我们发现S（0）= 0.116+/-0.003，接近最近用小角中子散射得到的S（0）= 0.0900+/-0.0048的实验值。需要更详细的实验和建模研究来确定假想温度和结构之间的关系。
英文摘要：
Liquids are in thermal equilibrium and have a non-zero static structure factor S(Q->0) = [<N^2>-<N>^2]/<N> = rho*k_B*T*Chi_T where rho is the number density, T is the temperature, Q is the scattering vector and Chi_T is the isothermal compressibility. The first part of this result involving the number N (or density) fluctuations is a purely geometrical result and does not involve any assumptions about thermal equilibrium or ergodicity and so is obeyed by all materials. From a large computer model of amorphous silicon, local number fluctuations extrapolate to give S(0) = 0.035+/-0.001. The same computation on a large model of vitreous silica using only the silicon atoms and rescaling the distances gives S(0) = 0.039+/-0.001, which suggests that this numerical result is robust and similar for all amorphous tetrahedral networks. For vitreous silica, we find that S(0) = 0.116+/-0.003, close to the experimental value of S(0) = 0.0900+/-0.0048 obtained recently by small angle neutron scattering. More detailed experimental and modelling studies are needed to determine the relationship between the fictive temperature and structure.
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