复杂不等价半导体AX/BY合金是由不等价二元半导体AX和BY形成的合金材料，能够有效减少晶格失配引起的内部应变对合金性质的影响，同时A-Y或B-X化学键可使其具有AX和BY所不具备的优异性能，如高效吸收可见光和良好的压电效应等。作为重要的可再生能源材料在固态发光照明、太阳能电池、光解水和压电器件等领域具有广阔的应用前景。本课题拟系统研究不等价合金的低温有序结构和高温无序结构，分析结构有序性对合金性质的影响和有序到无序的结构相变，得到组分与温度的相图。通过分析振动熵对合金稳定性的贡献，指出晶格振动效应对相图形状和不相混溶区温度的影响。采用动力学方法研究不同温度和压强作用下合金的结构演化，分析结构演化的具体路径、中间和终点结构的稳定性。在此基础上揭示能带结构和压电效应等性质与合金组分、温度和压强之间的定量关系，指出调节带隙和提高压电效应的有效方法，为扩展其在技术领域中的应用提供指导和参考。

Complex nonisovalent semiconductor AX/BY alloys are consist of binary semiconducts AX and BY, where the effects of internal strains induced by the lattice mismatch on the alloying properties can be effectively eliminated. It is the A-Y or B-X bonds that make the alloys possess more novel functions than AX and BY, such as the visible-light absorption and the enhancement of piezoelectricity. As the important renewable energy materials, they have widely potential applications in the technological fields of solid-state lighting, solar cells, water splitting and piezoelectric devices and so on. In this owrk, we will systematically investigate the low-temperature ordered and high-temperature disordered structures of alloys to show the effects of structural odering on the physical properties and the ordered-disordered phase transition, from which the alloying composition-temperature phase diagrams are plotted. We will show the effects of lattice vibrations on the phase diagram and the miscibility-gap temperature by taking into account the vibrational entropy. Meanwhile, we will also adopt the metadynamics method to study the structural evolution of alloys induced by temperature and pressure to show the detailed evolutionary pathways and the stability of intermediate and end-point structures. Finally, we will calculate the dependence of band structure, piezoelectric response and other properties on the alloying composition, temperature and pressure, thus to point out the feasible ways to tune the band gap and to enhance the piezoelectricity, which will be helpful in widening their technological applications.