第一性原理在热中子散射截面计算中的应用  

Application of First Principles in Calculation of Thermal Neutron Scattering Cross Section

作　　者：王立鹏[1] 张信一[1] 姜夺玉 胡田亮 曹璐 WANG Lipeng;ZHANG Xinyi;JIANG Duoyu;HU Tianliang;CAO Lu(Northwest Institute of Nuclear Technology,Xi’an 710024,China)

机构地区：[1]西北核技术研究所,西安710024

出　　处：《原子核物理评论》2023年第4期643-650,共8页Nuclear Physics Review

基　　金：国家自然科学基金资助项目(11905174,12275219)。

摘　　要：第一性原理被应用在核工程领域关注的热中子散射材料的热中子截面计算中。本工作以Al和Bi金属的热中子截面制作为例,分别基于第一性原理冷冻声子法和密度泛函微扰法,采用VASP结合PHONONY程序计算了它们的声子色散关系和声子态密度。基于NJOY程序,在LEAPR中添加Bi相干散射处理,制作了Al和Bi的热中子散射截面库。结果表明:对于Al,相较于冷冻声子法,密度泛函微扰理论的声子态密度得到的热中子散射截面与ENDF8.0符合更好,对于Bi,采用密度泛函微扰法消除了冷冻声子法的虚频现象,得到的热中子散射结果与实验值符合较好。本工作从探索材料内部特征机理的角度提出了一种更基础、更有预见性的制作热中子截面的方法,为研究新型反应堆的核材料热化机理奠定了理论基础。The calculation of thermal neutron cross section for thermal neutron scattering materials in the field of nuclear engineering is based on the first principle.This study utilizes Al and Bi metals as examples for the determination of thermal neutron cross sections.The frozen phonon method and density functional perturbation method are applied to calculate the thermal neutron cross sections for Al and Bi,respectively.Phonon dispersion relation and phonon density of state are computed using VASP and PHONONY.Subsequently,coherent scattering for Bi is incorporated into LEAPR using NJOY to generate the thermal neutron scattering cross-section libraries for Al and Bi.The results reveal that,in the case of Al,the thermal neutron scattering cross section obtained using the density functional perturbation theory is in better agreement with ENDF8.0 compared to the frozen phonon method.Conversely,for Bi,the density functional perturbation method eliminates the imaginary frequency phenomenon observed in the frozen phonon method,resulting in thermal neutron scattering results that align well with experimental data.The paper proposes a more fundamental and predictable method for generating thermal neutron crosssections by exploring the internal characteristic mechanism of the material,thus laying a theoretical foundation for studying the thermal mechanisms of new reactor nuclear materials.

关 键 词：第一性原理 声子态密度 热中子散射截面 核数据制作 

分 类 号：TL816.3[核科学技术—核技术及应用]