摘要
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Ag_3PO_4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Ag_3PO_4Mulliken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Ag_3PO_4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Ag_3PO_4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;Ag_3PO_4具有动力学稳定性特征;300～3 000 K范围内,Ag_3PO_4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1 200 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.
The stability of Ag3PO4 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 Ag3PO4. The Mulliken populations,energy band structures,density of states,phonon and phonon density of silver phosphate（ Ag3PO4） were calculated and analyzed by the firstprinciples 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,Ag3PO4 shows photodegradation and exhibits dynamic stability. The enthalpy and entropy of Ag3PO4 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 CVis about 93 cal / cell·K. The above conclusions are in good agreement with the experimental results.
作者
蔡维维
李蛟
张华
CAI Weiwei LI Jiao ZHANG Hua(School of Materials Science and Engineering, Shandong University of Technology, Zibo 255049, Chin)
出处
《材料科学与工艺》
EI
CAS
CSCD
北大核心
2016年第5期47-52,共6页
Materials Science and Technology
基金
山东省高等学校科技发展计划项目(J15LA08)
山东理工大学青年教师发展支持计划资助项目(4072-114019)
关键词
密度泛函理论
第一性原理
磷酸银
稳定性能
热力学性质
density functional theory
first-principles calculations
silver phosphate（Ag3PO4）
stability
thermodynamics properties
