[交流] crystal计算中输入文件关于能带的确定 已有1人参与

各位大神，小弟初学计算，在用crystal算晶体，在计算能带结构和态密度时（BAND和DOSS），下面是crystal网站给的示例 Example: MgO BAND structure     1.The first step is to define the number and position of the system bands. There are two atoms per unit cell, a Mg and an O, described by means of a 8-61G and 8-51G basis set, respectively, for a total of 18 atomic orbitals. Consequently, the number of bands is 18. All 18 bands are written in fort.25, saved by runprop as mgo.f25     2.The second step consists in the designation of a proper path in the Brillouin zone. MgO Bravais lattice is face-centered cubic (see the sheet documentation for the Brillouin zone of a face-centered cubic lattice).     3.The third step is the selection of the bands to be plotted. The number of electrons per cell is 20 and the core electrons are 12. This means that the lower six bands, which correspond to the core atomic orbitals, are flat, low in energy and not sensitively affected by the formation of the crystalline network. To investigate the energy region involved in the bond formation we can select the band from the 7-th to the 14-th. 其中关于第一点和第三点中总能带数和计算选择能带数是怎样确定的呢，比如说MgO，for a total of 18 atomic orbitals. Consequently, the number of bands is 18，有18个原子轨道就有18个能带么，后面3点又说we can select the band from the 7-th to the 14-th，为什么最多到14呢，这个选取的原则是什么呢？求教求教

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