Towey James J, Barney Emma R
Faculty of Engineering, University of Nottingham , University Park, Nottingham NG7 2RD, U.K.
J Phys Chem B. 2016 Dec 29;120(51):13169-13183. doi: 10.1021/acs.jpcb.6b08793. Epub 2016 Dec 15.
The structure of xAsSe-(1 - x)AsS glasses, where x = 1.000, 0.667, 0.500, 0.333, 0.250, and 0.000, is investigated using a combination of neutron and X-ray diffraction coupled with computational modeling using multicomposition empirical potential structure refinement (MC-EPSR). Traditional EPSR (T-EPSR) produces a set of empirical potentials that drive a structural model of a particular composition to agreement with diffraction experiments. The work presented here establishes the shortcomings in generating such a model for a ternary chalcogenide glass composition. In an enhancement to T-EPSR, MC-EPSR produces a set of pair potentials that generate robust structural models across a range of glass compositions. The structures obtained vary with composition in a much more systematic way than those taken from T-EPSR. For example, the average arsenic-sulfur bonding distances vary between 2.28 and 2.46 Å in T-EPSR but are 2.29 ± 0.02 Å in MC-EPSR. Similarly, the arsenic-selenium bond lengths from T-EPSR vary between 2.28 and 2.43 Å but are consistently 2.40 ± 0.02 Å in the MC-EPSR results. Analysis of these models suggests that the average separation of the chalcogen (S or Se) atoms is the structural origin of the changes in nonlinear refractive index with glass composition.
采用中子和X射线衍射相结合的方法，并结合使用多组分经验势结构精修（MC-EPSR）的计算模型，研究了xAsSe-(1 - x)AsS玻璃（其中x = 1.000、0.667、0.500、0.333、0.250和0.000）的结构。传统的经验势结构精修（T-EPSR）产生一组经验势，驱动特定组成的结构模型与衍射实验结果达成一致。本文所展示的工作揭示了为三元硫族化物玻璃组成生成此类模型时存在的缺陷。作为对T-EPSR的改进，MC-EPSR产生一组对势，可在一系列玻璃组成范围内生成可靠的结构模型。所获得的结构随组成的变化比从T-EPSR得到的结构更为系统。例如，T-EPSR中平均砷-硫键长在2.28至2.46 Å之间变化，而在MC-EPSR中为2.29 ± 0.02 Å。同样，T-EPSR中的砷-硒键长在2.28至2.43 Å之间变化，但在MC-EPSR结果中始终为2.40 ± 0.02 Å。对这些模型的分析表明，硫族（S或Se）原子的平均间距是非线性折射率随玻璃组成变化的结构根源。
