Density functional theory calculations within a DFT+U approach have been carried out to determine the effect of hydrostatic pressure and strain on the structural, electronic and magnetic properties of La_0.75Ca_0.25MnO₃. We investigate the opportunuty of the appearence of the A-type antiferromagnetic phase under pressure as observed from experiments. At ambient pressure and in the hydrostatic pressure regime (4–25 GPa), the system remains ferromagnetic in its ground state, and the A-type antiferromagnetic coupling is tied to Mn e _g orbital order while the ferromagnetic behavior refers to orbital disorder one. No magnetic transition was found when increasing the hydrostatic pressure up to 25 GPa. Applying a tetragonal distortion along the b direction of the pnma orthorhombic structure, the system exhibits a transition from the ferromagnetic orbitally disordered phase to the A-type antiferromagnetic orbitally ordered phase at about 22.5 GPa, in agreement with experiment. Projected density of states (PDOS) calculations predict the pressure and strain effects that are discussed in terms of different electronic occupations through and orbitals.

已在 DFT+U 方法中进行密度泛函理论计算，以确定静水压力和应变对 La _0.75 Ca _0.25 MnO ₃的结构、电子和磁性能的影响。我们研究了从实验中观察到的 A 型反铁磁相在压力下出现的机会。在环境压力和静水压力范围 (4-25 GPa) 下，系统在其基态保持铁磁性，并且 A 型反铁磁耦合与 Mn e _g 轨道有序而铁磁行为是指轨道无序之一。当静水压力增加到 25 GPa 时，没有发现磁性转变。沿pnma正交结构的b方向应用四方畸变，该系统在大约 22.5 GPa 处表现出从铁磁轨道无序相到 A 型反铁磁轨道有序相的转变，与实验一致。投影态密度 (PDOS) 计算预测压力和应变效应，这些效应是根据不同的电子占据和轨道进行讨论的。