五氧化二钽的基态结构及相图的理论研究

作为宽带隙半导体材料，五氧化二钽(Ta2O5)在多方面有重要的潜在应用。例如光学器件、新一代电子器件、能源及催化材料、超高精度测量仪器、抗腐蚀保护膜。尽管已有众多的研究，Ta2O5的基态结构尚无定论。在常压下，报道的Ta2O5结构相至少有10种，而关于各相之间的转变条件知之甚少。另一方面，Ta2O5晶体相的合成与生长非常依赖于实验条件。在本项目中，我们将采用第一性原理计算并结合当前先进的结构搜索算法，对Ta2O5的基态晶体结构以及压力-温度相图 (P-T相图) 作系统的研究。我们将主要关注在常压和高压条件下，Ta2O5的基态结构的共有特征；研究压力和温度诱导的结构相变，以及高压对Ta2O5电子结构的调控。基于理论计算的结果，建立起Ta2O5的P-T相图。我们的工作将揭示Ta2O5非富多彩的结构相之间的内在联系，为将来实验合成和进一步研究其物理和化学性质提供指引。

As a wide-gap semiconducting material, tantalum pentoxide (Ta2O5) has many important potential applications, including optical devices, the new-generation electronic devices, the materials for energy and catalysis, the instruments for ultraprecise measurement, and the corrosion resistant coatings. Despite the numerous research works, little consensus has been reached on the ground-state crystal structure of the low-temperature phase of Ta2O5. At ambient pressure, at least 10 different Ta2O5 phases are reported, while little is known about the structural transition among the phases. On the other hand, it is found that the obtained crystal structures of Ta2O5 depend critically on the experimental conditions (e.g., temperatures, pressures). In this project, we will carry out systematic and in-depth studies on the ground-state crystal structures and the pressure-temperature (P-T) phase diagram of Ta2O5, by using first-principles calculations in combination with state-of- the-art algorithms for structure search. Our research will be focused on the common features of the ground-state crystal structures at ambient and high-pressure conditions, and study the structural phase transitions induced by pressures and temperatures, as well as the pressure-dependence of the electronic structures of Ta2O5. Based on the theoretical results, the P-T phase diagram of Ta2O5 will be established. Our work will reveal the intrinsic connections among the rich phases of Ta2O5, and provide a guide map for future experimental synthesis and further studies on their physical and chemical properties.