共查询到18条相似文献,搜索用时 93 毫秒
1.
采用Lowdin方法计算了处于压缩状态的氦原子团簇He9体心立方向型的排斥势及其多体分量,并由此计算出团簇微观压强及其多体分压强。结果发现,多体作用对氦原子团簇He9压缩特性贡献较大。在相同体积下,由两体近似方法计算的体系压强比多原子体系实际压强偏高10%~30%;考虑三体分压强修正后,近似理论的计算值又会偏低1.5%~10%;只有同时考虑三体、四体修正后,近似理论计算值与实际多原子体系的压强值基本一致。团簇He9所表现出的压缩特性与固态氦的实验结果相符合。 相似文献
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运用从头计算自洽场方法和原子团簇理论计算了高压下固氦原子间的四体势分量.计算结果表明四体分量对结合能的贡献为正;随着压缩度增大四体势的贡献比例变大.采用两体、三体、四体势和Aziz吸引势计算固氦零温状态方程并与实验测量相比较,结果表明两体势对固氦的压缩性贡献了过多的正效应,加入三体分量的修正,仅在低于10GPa时理论值与实验值相符很好,但考虑了四体势修正后能将理论值与实验值符合程度提高到 27GPa.
关键词:
状态方程
固氦
四体势
从头计算 相似文献
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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—0.175 nm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—0.23 nm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—0.20 nm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—0.175 nm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.
关键词:
固氦
状态方程
多体相互作用 相似文献
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基于量子化学从头计算方法,计算了处于高密度条件下氮分子之间的两体排斥势和三体关联势,并采用球面平均近似求得了它们各自的高温平均势能值,得到了包括三体关联效应的等效两体势函数与分子间距的解析关系。借助分子流体微扰变分理论,并考虑van der Waals长程作用,分别采用总平均两体势和总等效两体势,计算了液氮的冲击压缩曲线。计算结果表明,在不需要考虑分子离解的压缩范围内(1~35 GPa),三体关联效应的贡献使分子间总等效两体势函数比单独两个分子间总平均作用势函数明显软化,与实验Hugoniot数据结果一致。 相似文献
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利用多体微扰理论(MBPT)计算了氦原子1snd(n=4—11)组态的1D—3D谱项分裂值.基于两种不同的模型分别计算Rayleigh-Shrdinger微扰展开式中仅含束缚态的部分和包含连续态的部分.对于束缚态,较严格地通过自洽迭代求解Hartree方程构造零级近似波函数,并利用积分处理方法对无穷项求和中的余项给出了近似算法.而对于连续态波函数,则采用简化的氢原子势模型.按照Rayleigh-Shrdinger微扰展开方法,将Rydberg态的微扰论修正计算至三级.计算表明,二级和三级微扰对谱项分裂的贡献主要来自于束缚态求和部分.单态-三重态精细结构分裂的计算结果与两组实验结果基本符合.
关键词:
氦原子
Rydberg态
多体微扰
组态波函数
能级分裂 相似文献
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The four-body Yakubovsky equations in a three-dimensional approach with the inclusion of the three-body forces are proposed.
The four-body bound state with two- and three-body interactions is formulated in the three-dimensional approach for identical
particles as a function of vector Jacobi momenta, specifically, the magnitudes of the momenta and the angles between them.
The modified three-dimensional Yakubovsky integral equations are successfully solved with the scalar two-meson exchange three-body
force, where the Malfliet-Tjon-type two-body force is implemented. The three-body force effects on the energy eigenvalue and
the four-body wave function, as well as accuracy of our numerical calculations are presented. 相似文献
12.
使用多重尺度法,解析地研究计及粒子间两体和三体同时作用下二维凝聚体中孤子的特性. 结果发现,当凝聚体粒子间两体作用为排斥、三体作用为吸引时,凝聚体内会产生暗孤子环,且随着三体吸引作用的减弱,暗孤子环中心峰的高度逐渐降低,并当三体吸引作用消失时暗孤子环演化为一个完美的二维暗孤子. 当两体和三体作用均为排斥时,凝聚体中的暗孤子的宽度和幅度随着三体排斥作用的加强而减小,且当三体作用强度增加到与两体作用同一数量级时,凝聚体产生坍塌现象.
关键词:
玻色-爱因斯坦凝聚体
两体和三体作用
暗孤子 相似文献
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It is found that the suppression due to two-body LambdaN-SigmaN coupling solves the overbinding problem in (5)(Lambda)He but it, in turn, causes a severe underbinding in the four-body systems. The shortage of this binding is overcome by introducing explicitly the Lambda-Sigma coupling which is equivalent to the LambdaNN three-body force. This three-body force becomes strong in the 0(+) states of (4)(Lambda)H and (4)(Lambda)He according to the coherently added enhancement. The 0(+)-1(+) splitting in (4)(Lambda)H and (4)(Lambda)He is found partly due to the LambdaN spin-spin interaction and partly due to the Lambda-Sigma coupling in the recent Nijmegen soft-core potential. 相似文献
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The energy as a function of density is calculated for neutron matter and for symmetrical nuclear matter, based on Jastrow trial wave functions. The energy expectation value is truncated in low cluster order. A detailed analysis of the two- and three-body cluster contributions and a special portion of the four-body contribution is given. Variation of a parameterized two-body correlation function is subjected to constraints designed to confine the trial wave function to the domain corresponding to rapid cluster convergence. Results are presented for a variety of model central potentials containing hard cores, for different sets of constraints, and for two- and three-parameter correlation functions. Calculations constrained by the “average Pauli condition” are found to yield results very close to those constrained by the “normalization” or “unitarity” condition, and the two-parameter correlation function appears to be quite adequate. The convergence of the cluster expansion, as reflected in the low orders, is good except at the highest densities considered. The three-body cluster contribution displays, in all cases, a remarkable internal cancellation between its “two-correlation-line” addends. 相似文献
15.
Effects of three-body interaction on collective excitation and stability of Bose--Einstein condensate
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This paper investigates the collective excitation and stability of
low-dimensional Bose--Einstein condensates with two- and three-body
interactions by the variational analysis of the time-dependent
Gross--Pitaevskii--Ginzburg equation. The spectrum of the low-energy
excitation and the effective potential for the width of the
condensate are obtained. The results show that: (i) the repulsive
two-body interaction among atoms makes the frequency red-shifted for
the internal excitation and the repulsive or attractive three-body
interaction always makes it blue-shifted; (ii) the region for the
existence of the stable bound states is obtained by identifying the
critical value of the two- and three-body interactions. 相似文献
16.
《Nuclear Physics A》1988,486(2):253-260
The inversion of the three energy equations, i.e. for the nuclear total energy, the sum of occupied single-particle state energies and the saturation condition, using the experimental data in 16O and 40Ca, is carried out to determine whether three-body effective interactions are necessary in addition to density independent and dependent two-body interactions. In order to fit the data both in a non-relativistic and a relativistic framework, the three-body interaction energy is found to be large and repulsive. We also show that density-dependent two-body effective interactions, which are another requisite in the non-relativistic potential theory, are not necessarily needed in the relativistic mean field framework but allow to increase the effective nucleon mass. 相似文献
17.
Chao-Qing Dai Deng-Shan Wang Liang-Liang Wang Jie-Fang Zhang W.M. Liu 《Annals of Physics》2011,(9):2356-2368
We investigate exact nonlinear matter wave functions with odd and even parities in the framework of quasi-two-dimensional Bose–Einstein condensates (BECs) with spatially modulated cubic–quintic nonlinearities and harmonic potential. The existence condition for these exact solutions requires that the minimum energy eigenvalue of the corresponding linear Schrödinger equation with harmonic potential is the cutoff value of the chemical potential λ. The competition between two-body and three-body interactions influences the energy of the localized state. For attractive two-body and three-body interactions, the larger the matter wave order number n, the larger the energy of the corresponding localized state. A linear stability analysis and direct simulations with initial white noise demonstrate that, for the same state (fixed n), increasing the number of atoms can add stability. A quasi-stable ground-state matter wave is also found for repulsive two-body and three-body interactions. We also discuss the experimental realization of these results in future experiments. These results are of particular significance to matter wave management in higher-dimensional BECs. 相似文献
18.
运用多体展开理论和量子化学方法—–超分子单、双(三重)激发微扰处理耦合簇CCSD(T)方法,首次系统地计算了面心立方固氪在较宽(从晶格平衡位置到体积压缩率超过3倍)区间的两体、三体和四体相互作用对结合能和物态方程的贡献大小,包括Hartree-Fock自洽场项和范德瓦耳斯长程关联作用项;并与实验数据进行比较.结果表明,在考虑到两体、三体、四体相互作用能后,多体展开理论以及CCSD(T)方法对平衡位置结合能测量数据0—130 GPa整个研究区间的实验物态方程数据都做出令人满意的描述. 相似文献