原文如下：

Get esd's on geometric measurements

Olex2 can calculate esd's on a variety of geometric measurements, also if a CIF is loaded into Olex2 then esd's available in the CIF (bond lengths and the angles) will be displayed in the tooltip when hovering over the bonds or selection of the bonds; use the 'sel' command to print the values in the console.

To calculate the esd's Olex2 need the variance-covariance matrix. This can be readily produced by shelxl when refining with a negative MORE instruction (like MORE -1). It also will be soon available from the smtbx refinement. Once the matrix file is available, the geometric parameters can be easily calculated by selecting:

a bond or two atoms – length two bonds or three atoms – angle four atoms - torsion angle and the tetrahedron volume a plane - RMSD and the centroid coordinates in fractional and Cartesian coordinates a plane and an atom - atom to plane and atom to plane centroid distances a plane and a bond - angle between the plane normal and the bond two planes - angle between the plane normals, plane centroid to plane centroid, plane to centroid and the shift between the plane centroids distances three planes - the angle between the plane centroids

Then type:

>>esd

to get the measurements with esd's.

Note that the current implementation of the esd calculation procedure does not consider symmetry constraints and gives esd's even for the symmetry related parameters.

译文如下：

3.9. 获取几何测量的估计标准偏差(esd)

Olex2可以计算各种几何测量的估计标准偏差(esd, Estimated Standard Deviation)，若将CIF加载到Olex2中，当鼠标悬停在键或选定键上时，工具提示中将显示CIF中可用的esd(键长和角度)；使用'sel'指令在控制台中打印这些数值。

为计算esd，Olex2需要方差-协方差矩阵。当使用负的MORE指令(如MORE -1)进行精修时，shelxl可很容易地获得所需方差-协方差矩阵。它也很快将从smtbx精修中提供。一旦矩阵文件可用，几何参数可以很容易地通过以下选择进行计算：

一根键或两个原子——键长(距离)

两根键或三个原子——键角

四个原子——扭转角和四面体体积

一个平面——RMSD和质心的分数坐标和笛卡尔坐标

一个平面和一个原子——原子到平面距离和原子到平面质心距离

一个平面和一根键——平面法线与该键夹角

两个平面——两个平面法线夹角、两个平面质心间距、平面到质心间距以及两个平面质心滑移间距

三个平面——三个平面质心形成的夹角

然后键入

>>esd

以获取上述测量的esd。

请注意，esd计算程序的当前执行程序没有考虑对称性，甚至对对称性相关参数也给出了esd。

本文辅助视频如下：

Olex2视频教程——指令sel的应用

https://www.bilibili.com/video/BV1ib411u7r2

Olex2视频教程——指令mpln的使用

https://www.bilibili.com/video/BV1ob411W79i

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