Abstract In order to figure out the effect of excess Mn atoms on the preference of the martensite structure, the tetragonal distortion was employed in the off-stoichiometric Ni-Mn-In alloys with different Mn contents using the Extra Muffin-tin Orbital combined with the Coherent Potential Approximation (EMTO-CPA). The calculations were conducted with the optimization of the magnetic structure, where the stoichiometric Ni2MnIn alloy was served as the reference. The ground state-energy-resolved tetragonal distortion reveals that the excess Mn changes the preferred stable structure from the perfect cubic L21 structure to the tetragonally distorted structures. The stable tetragonal structure could shift from c/a 1 with the increase of the Mn concentration. Furthermore, to find out more accurate preference of the martensite structure, the formation energies were calculated using different relaxation methods. The chemical disorder method with a 4-atom cell was used for the tetragonal L10 structure by the EMTO-CPA, and the supercell method with a 96-atom cell was applied for the orthorhombic structure by the VASP at 0 K in their ferromagnetic state. The results show that, compared with the perfect cubic L21 structure of the stoichiometric Ni2MnIn alloy, the orthorhombic structure is preferred at lower Mn concentrations (between 29 at. % and 40 at. %), whereas the tetragonal L10 structure is more stable at the higher Mn concentrations (above 40 at. %). Moreover, the effect of the Mn concentration on the magnetic properties was also studied. With the increase of excess Mn content, the magnetic moment increases linearly in the ferromagnetic cubic L21 structure, whereas it varies in the two kinds of martensite. The excess Mn could lead to the coexistence of ferromagnetism and antiferromagnetism. The appearance of the antiferromagnetism could be attributed to the Ni-Mn antiferromagnetic interaction in the tetragonal martensite.

中文翻译：

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非化学计量Ni-Mn-In合金马氏体组织的第一性原理计算研究

摘要 为了研究过量 Mn 原子对马氏体结构偏好性的影响，采用 Extra Muffin-tin Orbital 结合马氏体结构，在不同 Mn 含量的非化学计量 Ni-Mn-In 合金中进行四方畸变。相干电位近似 (EMTO-CPA)。计算是通过优化磁结构进行的，其中化学计量的 Ni2MnIn 合金作为参考。基态能量分辨的四方畸变表明，过量的 Mn 将优选的稳定结构从完美的立方 L21 结构改变为四方畸变结构。随着Mn浓度的增加，稳定的四方结构可以从c/a 1 转变。此外，为了找出更准确的马氏体结构偏好，使用不同的弛豫方法计算形成能。EMTO-CPA 使用 4 原子晶胞的化学无序法处理四方 L10 结构，VASP 在 0 K 的铁磁状态下将具有 96 原子晶胞的超晶胞法用于正交结构。结果表明，与化学计量的 Ni2MnIn 合金的完美立方 L21 结构相比，在较低 Mn 浓度（29 at.% 和 40 at.% 之间）时优选正交结构，而四方 L10 结构在 Mn 浓度下更稳定。更高的锰浓度（高于 40 原子百分比）。此外，还研究了Mn浓度对磁性能的影响。随着过量Mn含量的增加，铁磁立方L21结构中的磁矩线性增加，而它在两种马氏体中有所不同。过量的Mn会导致铁磁性和反铁磁性共存。反铁磁性的出现可归因于四方马氏体中的 Ni-Mn 反铁磁相互作用。