Determination of Site Occupancy in Multiply-Occupied Atomic Sites

9804768 Hughes在具有多个占据原子位置的晶体中的原子的位置分配可以使用键价方法唯一地确定。 我们发现，加权计算的价和最接近的加权形式价的网站分配产生良好的协议与化学分析。 对于任何晶体，该方法需要结构数据和电子计数的网站上的问题;此外，如果化学分析是可用的，这些数据可以纳入该方法。该方法通过改变每个潜在取代基的分数占位率来最小化观察到的和计算出的键价总和与观察到的和计算出的电子占位率之间的差异的平方和;还可以添加用于建模化学分析的术语，并且通过最小化价能来计算最佳解。 赠款将用于评估模型本身，并在矿物实例上进行广泛测试。 此外，由于所要求的资金支持的学生在致残性中风后重返科学，研究的一个重要成果将是观察残疾人的科学能力。

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.