It could form in any direction because the Coulombic field is radial in all directions.

能够在任何方向形成,因为库仑产在全方位发生分散。

麻省理工公开课 - 固态化学导论课程节选

I am only counting in one direction, 2 so I have to multiply this whole thing by two because I have to count both directions.

因为我只是在一个方向上计数，所以我要把这些所有乘以,因为我们必须考虑到2个方向。

麻省理工公开课 - 固态化学导论课程节选