BCC金属弹性及热力学性质随温度变化的理论计算  

Theoretical studies of the elastic and thermodynamic properties of BCC metals with temperature

作　　者：刘瑞萍 肖理君 郝璐瑶 李秀燕 杨致 徐利春 BCC metals with temperatureLIU Ruiping, XIAO Lijun, HAO Luyao, LI Xiuyan, YANG Zhi, XU Lichun(College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China)

机构地区：[1]太原理工大学物理与光电工程学院,太原030024

出　　处：《中国科技论文》2018年第5期511-516,共6页China Sciencepaper

基　　金：国家自然科学基金资助项目(51401142)

摘　　要：基于密度泛函第一性原理计算了体心立方金属Ta、Fe、W、Mo的弹性和热力学性质。使用2种不同的交换关联泛函广义梯度近似(general gradient approximate,GGA)和局域密度近似(local density approximation,LDA)计算了T=0K时Ta、Fe、W、Mo的晶格常数和弹性常数,发现使用GGA与实验值符合较好,说明在计算弹性常数时选择合适的交换关联泛函对计算弹性常数的准确度十分重要。通过密度泛函理论(density functional theory,DFT)和密度泛函微扰理论(density-functional perturbation theory,DFPT)计算得出弹性常数随温度的升高而降低,并通过力学稳定判断标准得到Ta、Fe、W、Mo在0~1 500K时晶格结构稳定,不发生相变。此外,通过计算得出的体积模量B和剪切模量G的比值B/G判断出Ta、Fe、W、Mo在0~1 500K表现为韧性。并预测了Ta、Fe、W、Mo的热膨胀系数、等压热容、等容热容与温度的关系,发现在低温区域(0~300K)等容热容遵循T3定律,在高温区域(1 000~1 500K)遵循能量均分定律,证明了计算方法的合理性。Based on the density functional theory,the elastic and thermodynamic properties of BCC metals have been calculated by using the first-principles method.Firstly,the lattice constants of BCC metals are optimized by using two different exchange correlation functions：general gradient approximate（GGA）and local density approximation（LDA）at 0 K.Compared with the results from LDA,the results from the GGA-PAW are more closer to the experimental results.Therefore,it is important to choose appropriate exchange correlation function.Secondly,based on the density functional theory（DFT）and density-functional perturbation theory（DFPT）,calculation shows the elastic constant decreases with the increase of temperature.The temperature-dependence elastic constants indicate that BCC phase Ta,Fe,W,Mo are mechanically stable.In addition,the ratio of bulk modulus to shear modulus（B/G）has been studied.It is indicated that the four metals all show the toughness at the temperature of 0-1 500 K.Last,the thermodynamic properties including the thermal expansion coefficients,heat capacity at constant volume CV,the isobaric heat capacity CPare predicted.It is found that heat capacity at constant volume follows T3 theorem in low temperature（0-300 K）,and follows the equipartition theorem in high temperature（1 000-1 500 K）,which can prove the rationality of the calculation method.

关 键 词：体心立方金属 热力学性质 弹性常数 温度 密度泛函理论 

分 类 号：O522.2[理学—高压高温物理]