The stability of Ag3 PO4 remains a major problem, and the related theoretical research is still scarce. Moreover, it is difficult to obtain some thermodynamic properties of Ag3PO4, such as entropy, enthalpy and free energy by experimental method. Based on the above issues, this paper aims to theoretically investigate the stability and thermodynamics properties of Ag3 PO4 . The Mulliken populations, energy band structures, density of states, phonon and phonon density of silver phosphate ( Ag3 PO4 ) were calculated and analyzed by the first⁃principles method using plane⁃wave norm conserving pseudo⁃potential calculation based on density functional theory. The results show that Ag ion plays an important role in the crystal. The formation of stable tetrahedral PO4 with P—O and O—O bonds weakens the covalent Ag—O bonds, resulting in a metastable state of the Ag ion. Then, the metastable Ag ions are easy to get rid of the oxygen ions and obtain electron to form metallic silver. Therefore, Ag3 PO4 shows photodegradation and exhibits dynamic stability. The enthalpy and entropy of Ag3 PO4 increase nonlinearly with the increase of temperature in the range of 300~3 000 K while free energy decreases. When temperature reaches 1 200 K, the value of CV is about 93 cal/cell·K. The above conclusions are in good agreement with the experimental results.%磷酸银差的稳定性能是限制其发展的主要瓶颈，与之相关的理论研究依然匮乏；同时，通过实验手段难以获得描述Ag3 PO4熵、焓、自由能等热力学性质的相关信息．基于上述问题，本文从理论上探讨了磷酸银稳定性能与热力学性质．基于密度泛函理论的第一性原理，应用规范－守恒赝势平面波方法，对Ag3 PO4 Mulliken布居、能带结构、态密度以及声子谱、声子态密度进行了计算分析．研究结果表明：P—O、O—O间共价健的存在导致Ag3 PO4原胞中易形成稳定PO4四面体结构，该结构能够弱化Ag—O健合力，使Ag＋处于亚稳态；当Ag3 PO4接触光生电子时，Ag＋易摆脱O2－束缚获得电子形成单质银而表现出光不稳定性；Ag3 PO4具有动力学稳定性特征；300～3000 K范围内，Ag3 PO4晶体体系熵、焓随温度增加呈非线性增加，自由能下降，等容热容CV在1200 K时达到恒定，约为93 cal／cell·K．上述计算结果与实验结果吻合．
展开▼
