由于具有磁结构耦合特性的MnCoGe基合金可以表现出巨磁热、压热效应，因此调控磁和结构相变逐渐成为近年来关注的焦点。但是，目前人们对于该体系下的相变调控机理尚不清楚。申请者在前期的研究中发现，价电子浓度并不是调控MnCoGe基合金相变的关键因素，体系内部原子局域环境的改变应该起到更为关键的作用。为此，本项目以MnCoGe基合金为研究对象，通过引入空位与化学压力来调控体系的相变，找出原子间距与化学压力和空位量的变化规律，掌握并总结出磁结构耦合体系晶格和键长的特点；通过第一性原理计算手段来研究体系电子结构和差分电子密度，找出化学压力和空位引起体系电子结构和能带的改变，揭示调控MnCoGe基合金马氏体结构相变微观机理。在此基础上，理论上设计出具有磁结构耦合特性的MnCoGe基合金的通用模型，针对该模型来探索晶格畸变与原子局域环境影响磁结构耦合的深层次原因，从而认识巨磁热、压热效应的根源。

Recently, controlling the magnetic and structural transition of MnCoGe-based alloys has become a new focus of attention due to the giant magnetocaloric and barocaloric effects that these alloys can display. However, the physical mechanism of phase regulation is not clear yet. In our previous research, it is found that the valence-electron concentration e/a ratio is not the critical factors for the phase regulation of MnCoGe-based alloys but the change of inner atom surroundings plays an more important role. Therefore, MnCoGe-based alloys are taken as the mainly research purpose of this project. Through the introducing of the vacancy and chemical pressure, it is expected that the varied law of the atomic chain and chemical pressure can be found, and characteristic of lattice and atom bond can be grasped. By analyzing the electronic structure and electron state density by first principle calculations, the changing of electronic structure and energy band induced by chemical pressure and atom vacancy can be found, revealing the microscopic mechanism of regulation of MnCoGe-based alloy martensitic structural transformation. And based on the facts above, the general model of MnCoGe-based alloy with magneto-structural transition can be designed theoretically. Finally the further reason of magneto-structural transition causing by lattice distortion and atom surroundings changing can be explored and moreover the origin of giant magnetocaloric and barocaloric effects can be understood.