N2–N2 interaction potential from ab initio calculations, with application to the structure of (N2)2
N2–N2 interaction potential from ab initio calculations, with application to the structure of (N2)2
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从头算起的 N2-N2 相互作用势，并应用于 (N2)2 的结构
DOI：
10.1063/1.439067
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发表时间：
1980
影响因子：
4.4
通讯作者：
A. Avoird
中科院分区：
文献类型：
--
作者：
R. Berns;A. Avoird
短程静电和（一阶）交换对 N2-N2 相互作用能的贡献已作为 N2 方向和距离（139 个几何形状）的函数进行了计算。使用数值积分程序，结果以球面展开的形式进行分析表示。在 R=0.3 nm 处，如果我们包括前 18 个独立项，则该扩展的精确度优于 0.5%；如果我们在 L A =L B =4 之后截断，则该扩展精确到 2%；如果我们在 L A =L B =2 之后截断，则该扩展精确到 16%。结合Mulder等人计算的长程多极展开结果（静电R -5、R -7、R -9项，色散R -6、R -8、R -10项），这在范德华最小值区域产生了各向异性的N2-N2相互作用势，这也可以通过位点模型很好地表示。该势与固体 N2 气相和有序（α 和 γ）晶相的现有实验数据非常一致。讨论了范德华分子(N2)2的结构；对于交叉结构，其能量最低：ΔE m =1.5 kJ/mol，R m =0.35 nm（对于各向同性势，井特性为 ΔE m =0.75 kJ/mol 和 R m =0.417 nm）。 （交错的）平行结构和T形结构的能量稍高。内部 N2 旋转势垒从 0.2 kJ/mol (17 cm−1) 到与解离能相当的值不等。
The short range electrostatic and (first order) exchange contributions to the N2–N2 interaction energy have been calculated a b i n i t i o as a function of the N2 orientations and the distance (139 geometries). Using a numerical integration procedure, the results have been represented analytically in the form of a spherical expansion. At R=0.3 nm this expansion is accurate to better than 0.5% if we include the first 18 independent terms, to 2% if we truncate after L A =L B =4, and to 16% if we truncate after L A =L B =2. In combination with the long range multipole expansion results (electrostaticR −5, R −7, R −9 terms, dispersion R −6, R −8, R −10 terms) calculated by Mulder e t a l., this yields an anisotropic N2–N2 interaction potential in the region of the van der Waals minimum, which can be fairly well represented also by a site–site model. The potential is in good agreement with the available experimental data for the gas phase and for the ordered (α and γ) crystal phases of solid N2. The structure of the van der Waals molecule (N2)2 is discussed; its energy is lowest for the crossed structure: ΔE m =1.5 kJ/mol, R m =0.35 nm (for the isotropic potential the well characteristics are ΔE m =0.75 kJ/mol and R m =0.417 nm). The (staggered) parallel and the T‐shaped structures are slightly higher in energy. The internal N2 rotation barriers vary from 0.2 kJ/mol (17 cm−1) to values comparable with the dissociation energy.