We investigate the changes in the electronic structure and magnetic properties of BiMnO${}_{3+\delta }$ accompanied the phase transition $C2∕c\to P{2}_1∕c$ which occurs either with an increase in the oxygen content or with external pressure applied. We have established that although both factors lead to similar structural changes, their mechanisms have reverse causal relationships. The application of pressure leads to the change in the volume of MnO${}_6$ octahedra. The latter, due to strong $p$-$d$ hybridization, leads to a decrease in the localization degree of manganese electrons, which causes the reduction in Mn magnetic moments. Meanwhile, when there is excess oxygen in the system, the reverse process occurs wherein the charge density redistribution leads to a decrease in the occupation number of the Mn-$e_g$ states causing the drop in the value of the local magnetic moments and, as a consequence, to the contraction in the lengths of the Mn-O bonds.

我们研究了 BiMnO 的电子结构和磁性能的变化${}_{3+\delta }$ 伴随相变 $C2∕C\to 磷2_1∕C$这发生在氧含量增加或施加外部压力时。我们已经确定，虽然这两个因素导致类似的结构变化，但它们的机制具有反向因果关系。施加压力导致MnO的体积发生变化${}_6$八面体。后者，由于强$磷$——$d$杂化，导致锰电子的局域化程度降低，从而导致锰磁矩降低。同时，当系统中存在过量氧气时，会发生相反的过程，其中电荷密度重新分布导致Mn-的占据数减少。${\mathrm{电子}}_G$ 导致局部磁矩值下降的状态，从而导致 Mn-O 键长度的收缩。