An integer minimal principle and triplet sieve method for phasing centrosymmetric structures.
An integer minimal principle and triplet sieve method for phasing centrosymmetric structures.
复制标题
用于定相中心对称结构的整数极小原理和三重态筛法。
DOI：
10.1107/s0108767307000621
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Sahinidis,NikolaosV
中科院分区：
文献类型：
--
作者：
Smith,AlexanderB;Xu,Hongliang;Sahinidis,NikolaosV
本文提出了一种新的中心对称结构的整数极小原理模型，该模型充分考虑了非对称空间群中存在的互易空间相移。此外，该模型的伪极小值的刻画是根据偶数和奇数三元组来完成的。在此基础上，提出了一种三重筛法。首先，仅使用可靠三元组的子集的高斯消除被用于定相。三重子集是使用逐渐变小的最强反射集生成的。通过列举存在的自由度来生成几个阶段解集。为了便于对这些相溶液的质量进行计算评估，这些相集被传递到结晶学软件SNB中，该软件在两个循环中展开反射集。最终的解决方案是通过统计两个结晶学优值系数来确定的。给出了各种结构的计算结果。
In this paper, a new integer minimal principle model for centrosymmetric structures is presented; one which fully accounts for reciprocal-space phase shifts present in non-symmorphic space groups. Additionally, characterization of false minima of the model is done in terms of even and odd triplets. Based on this characterization, a triplet sieve method is proposed. First, Gaussian elimination using only a subset of reliable triplets is employed for phasing. Triplet subsets are generated using a progressively smaller set of the strongest reflections. Several phase solution sets are generated by enumerating the degrees of freedom present. To facilitate computational evaluation of the quality of these phase solutions, these phase sets are passed into the crystallographic software SnB, which expands the reflection set in two cycles. The final solution is identified via statistics of two crystallographic figures of merit. Computational results are presented for a variety of structures.