Determination of Site Occupancy in Multiply-Occupied Atomic Sites

9804768Hughes具有多占据原子位置的晶体中原子的位置分配可以用键价方法唯一地确定。我们发现，加权计算价和最接近加权形式价的位置分配与化学分析结果非常一致。对于任何晶体，该方法都需要有关位置的结构数据和电子计数；此外，如果可以进行化学分析，则可以将这些数据合并到方法中。该方法通过改变每个潜在取代基的位置占有率来最小化观察和计算的键价和与观察和计算的电子占有率之差的平方和；还可以添加用于模拟化学分析的项，并通过最小化价能来计算最优解。授予的资金将用于评估模型本身，并在矿物样品上对其进行广泛测试。此外，由于由所要求的资金支持的学生在中风后重返科学领域，这项研究的一个重要成果将是观察到为残疾人提供科学知识。

9804768HughesSite assignment of atoms in crystals with multiply-occupied atomic sites can be determined uniquely using the bond valence method. We find that site assignments in which the weighted calculated valence sums are closest to the weighted formal valences yield excellent agreement with the chemical analysis. For any crystal, the method requires structure data and electron count for the sites in question; furthermore, if chemical analyses are available, these data may be incorporated into the method. The method minimizes the sum of squares of the difference between observed and calculated bond valence sums and observed and calculated electron occupancy by varying the fractional site occupancy for each potential substituent; terms for modeling chemical analyses can also be added, and the optimum solution is calculated by minimizing valence energy. Granted funds will be used to evaluate the model itself and test it extensively on mineral examples. Furthermore, because the student supported by the requested funds is returning to science after a disabling stroke, an important outcome of the research will be observations of enabling science to the disabled.