In this work, we report on the structural, electronic, and ferroelectric properties of SmMn₂O₅ by using first-principles density functional theory plus on-site Coulomb interaction (DFT + U) calculations. A thorough analysis was preformed to reveal the competing characteristics of different high-temperature (T) phases and the polarization mechanism in the low-T multiferroic phase. We show that the structural characteristics of the high-T phases have a strong influence on the low-T multiferroicity. In addition to the spin-induced lattice distortion that reduces substantially the purely electronic ferroelectricity, the dominant polarization mechanism in low-T SmMn₂O₅ still originates from the electronic polarization. By performing mode decomposition of the Hellmann–Feynman forces and the lattice distortion induced by the q = (0.5, 0, 0) magnetic order, we find that the Raman-active A_g mode characterized by the Mn⁴⁺O₆ octahedron distortion and synergistic displacement of Mn³⁺ and Sm ions is of primary importance, while the infrared (IR)-active B_2u mode plays a secondary role. These findings provide a theoretical foundation for future studies concerning the enhanced magnetoelectric effects of SmMn₂O₅ due to its pure exchange–striction mechanism.

在这项工作中，我们通过使用第一性原理密度泛函理论加上现场库仑相互作用 (DFT +  U ) 计算来报告 SmMn ₂ O ₅的结构、电子和铁电性质。进行了彻底的分析，以揭示不同高温（T）相的竞争特性和低T多铁性相中的极化机制。我们表明，高T相的结构特征对低T多铁性有很大影响。除了显着降低纯电子铁电性的自旋诱导晶格畸变之外，低-T SmMn ₂ O ₅仍然源于电子极化。通过执行赫尔曼力的模式分解和由感应晶格畸变q =（0.5，0，0）磁顺序，我们发现，所述拉曼活性甲_克模式，其特征在于Mn的⁴⁺ ø ₆八面体的失真和Mn ³⁺和Sm 离子的协同置换是最重要的，而红外（IR）活性B _{2 u}模式起次要作用。这些发现为未来关于 SmMn ₂ O增强磁电效应的研究提供了理论基础₅由于其纯粹的交换限制机制。