U和UO2状态方程研究进展

Research Progress of Equation of State for Uranium and Uranium Dioxide

铀和二氧化铀都是核科学与核工程中的重要材料,长期以来都不缺乏对它们的状态方程的研究。它们生产、存储和使用的环境复杂,涵盖宽温、宽压、强辐照、表面辐射、氦泡演化等极端条件,需要从实验和理论出发获取不同温度和压力下的材料物性,如晶体结构、相变行为、压缩性质、弹性性质与输运性质。此外,它们都属于强关联电子体系,拥有丰富的相图与奇特的物理性质,因此在实验与理论上研究它们的状态方程等物性具有极大的挑战性,该项研究一直属于前沿研究的热点。数十年来,人们采取各种实验手段,对铀和二氧化铀的热力学物性进行了测量;但由于铀及其化合物的特殊性质,相关实验研究工作仍存在一定程度上的困难。而另一方面,自1990年代以来,随着第一性原理方法的发展,使用密度泛函理论(DFT)方法对铀和二氧化铀物理性质展开计算的工作也不断涌现,不仅与实验工作相互验证,而且填补了实验条件无法企及的极端条件下的参数空白。随着计算机软硬件和数值算法的发展,相关DFT方法已经获得了较大突破,对铀和二氧化铀状态方程的描述也更为准确。其中,修正电子多体关联效应的动力学平均场方法(DMFT)以及修正声子振动能的平均场势方法(MFP)等算法是值得研究者进一步关注的。本文就20世纪以来对金属铀和二氧化铀实验和理论状态方程的研究进展进行了梳理,先后针对实验测量和理论计算两方面的晶体结构和相变行为、准静态压缩与冲击绝热压缩曲线、弹性力学、输运性质进行了概括总结,并探讨了二氧化铀晶体缺陷行为的相关研究工作。此外,本文还利用第一性原理方法对铀和二氧化铀的状态方程做了简要的计算,验证了已有公开文献中的结果,这将有助于后续研究。

Uranium and uranium dioxide are important materials in nuclear science and nuclear engineering,and there has been no lack of research on their equations of state for a long time.The environment for their production,storage,and use is complex,covering extreme conditions such as wide temperature,wide pressure,strong radiation,surface radiation,and helium bubble evolution.It is necessary to experimentally and theoretically obtain the physical properties of materials at different temperatures and pressures,such as crystal structure,phase transition behavior,compression properties,elastic properties and transport properties.In addition,they are all strongly correlated electronic systems with rich phase diagrams and peculiar physical properties.Therefore,experimentally and theoretically studying their physical properties,such as equations of state,is extremely challenging and has always been a hot issue in frontier research.Over the past decades,various experimental methods have been used to measure the physical properties of uranium and uranium dioxide;however,due to the special properties of uranium and its compounds,there is a certain degree of difficulty in their experimental measurement.On the other hand,since the 1990s,with the development of first-principles methods,the calculation of the physical properties of uranium and ura-nium dioxide using the density functional theory(DFT)method has also emerged,which can be a useful addition to experimental data.With the development of computing power and calculation methods,correction methods based on the DFT method have been proposed,and the description of the uranium and uranium dioxide equations of state has become more accurate.Among them,the dynamical mean-field theory(DMFT),the mean-field potential(MFP)and other algorithms are worthy of our further attention.This article summarizes the research progress of experimental and theoretical equations of state of metallic uranium and uranium dioxide since the last century,summarizes the properties of crystal structure and phase transition behavior,quasi-static and impact adiabatic compression curve,elastic and transport properties of experimental measurement and theoretical calculation,respectively,and additionally discusses the uranium dioxide crystal defect behavior.At the same time,we use first-principles methods to make a brief calculation of the equations of state of uranium and uranium dioxide,verify the results in the existing public literature,and help subsequent related research.