多体相互作用对高压固氦状态方程的影响  

Many-body contributions to the equation of state for highly compressed solid helium

作　　者：田春玲[1] 刘福生[2] 蔡灵仓[1] 经福谦[1] 

机构地区：[1]中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室 [2]西南交通大学高压物理实验室,成都610031

出　　处：《物理学报》2006年第2期764-769,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10376027);国防科技实验室基金(批准号:51478678905ZS7501);武器装备预研基金(批准号:51478030203QT2201);西南交通大学博士创新基金资助的课题.~~

摘　　要：采用量子化学自洽场方法及原子团簇理论对固氦晶格原子势能进行多体展开,定量确定了最近邻原子间距R在0·26—0·175nm之间,短程的两体到五体相互作用对晶体结合能及压缩特性的贡献,并对不同间距下多体展开式的截断位置进行了讨论.结果表明:当最近邻原子间距R在0·26—0·175nm之间取值,在具有hcp相结构的晶格中,氦原子势能的多体展开式是一收敛的交错型级数,该级数中两体项、四体项为正值,而三体项、五体项为负值.当R在0·26—0·23nm之间取值时,仅保留级数中两体和三体项就能很好地描述晶格原子势能;当R在0·23—0·20nm之间取值,多体展式需要展开到四体相互作用项;当R在0·20—0·175nm之间取值必须再加入五体项贡献.考虑到五体相互作用后,理论计算已能圆满地解释目前固氦等温压缩数据,其最大压力达60GPa.To investigate the significance of various many-body effects on the equation of state （EOS） of solid helium, the interaction energy of hcp crystal structure is expanded as a sum of two- to five-body potentials in the present work. Each short-range many- body term between helium atom clusters is computed by means of Hartree-Fock （HF） self-consistent-field （SCF） method. It is indicated that at high densities the many-body expansion formula is an alternative series, in which two-, and four-body terms are positive, whereas three- and five-body terms are negative. According to such an expansion of crystal interaction energy, the equation of state of solid helium at 0 K is obtained. The specific characteristics of each of the up to five-body contributions in highly compressed helium are discussed. Between 0.26 to 0.23nm, the interaction energy may be well described by two- and three-body interactions. Over a distance range 0.23-0.20nm, truncated many-body expansion after the four-body term recovers the main part of atomic potential energy. Below 0.20nm the five-body contributions have to be included. The sum of two- to five- body term accurately reproduces the atomic potential energy from 0.20 to 0. 175nm. The inclusion up to five-body potential satisfactorily describes the available experimental data from 7.5 to 2.5 cm^3/mol, corresponding to 1-60 GPa.

关 键 词：固氦 状态方程 多体相互作用 

分 类 号：O562.4[理学—原子与分子物理]