Stoichiometric change and solid decomposition in Ca–S compounds under high pressure  

作　　者：Yang Lv Jian-Fu Li Zhao-Bin Zhang Yong Liu Jia-Nan Yuan Jia-Ni Lin Xiao-Li Wang 吕阳;李建福;张钊彬;刘勇;袁嘉男;林佳妮;王晓丽

机构地区：[1]School of Physics and Electronic Information,Yantai University,Yantai 264005,China

出　　处：《Chinese Physics B》2025年第4期92-100,共9页中国物理B(英文版)

基　　金：Project supported by the National Natural Science Foundation of China(Grant Nos.11974154 and 12304278);the Taishan Scholars Special Funding for Construction Projects(Grant No.tstp20230622);the Natural Science Foundation of Shandong Province(Grant Nos.ZR2022MA004,ZR2023QA127,and ZR2024QA121);the Special Foundation of Yantai for Leading Talents above Provincial Level.

摘　　要：As an independent thermodynamic parameter,pressure significantly influences interatomic distances,leading to an increase in material density.In this work,we employ the CALYPSO structure search and density functional theory calculations to explore the structural phase transitions and electronic properties of calcium-sulfur compounds(Ca_(x)S_(1-x),where x=1/4,1/3,1/2,2/3,3/4,4/5)under 0-1200 GPa.The calculated formation enthalpies suggest that Ca_(x)S_(1-x)compounds undergo multiple phase transitions and eventually decompose into elemental Ca and S,challenging the traditional view that pressure stabilizes and densifies compounds.The analysis of formation enthalpy indicates that an increase in pressure leads to a rise in internal energy and the PV term,resulting in thermodynamic instability.Bader charge analysis reveals that this phenomenon is attributed to a decrease in charge transfer under high pressure.The activation of Ca-3d orbitals is significantly enhanced under pressure,leading to competition with Ca-4s orbitals and S-3p orbitals.This may cause the formation enthalpy minimum on the convex hull to shift sequentially from CaS to CaS3,then to Ca_(3)S and Ca_(2)S,and finally back to CaS.These findings provide critical insights into the behavior of alkaline-earth metal sulfides under high pressure,with implications for the synthesis and application of novel materials under extreme conditions and for understanding element distribution in planetary interiors.

关 键 词：high pressure calcium sulfide STOICHIOMETRY solid decomposition 

分 类 号：O641[理学—物理化学]