Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
J Phys Chem A. 2010 Aug 26;114(33):8505-16. doi: 10.1021/jp908835v.
Calculations using the full configuration interaction and coupled cluster methods are combined to yield a realistic curve for the helium dimer by extrapolation to the complete basis set limit. Extrapolations of the full configuration interaction energies alone are also done by reassignment of the basis hierarchic numbers. In no case has the common procedure of correcting the energies for the basis set superposition error by counterpoise been employed. The curves so generated agree well with the best available estimates, in one case within 1 cK (centikelvin) at the minimum. This corroborates our previous finding that such an approach provides an alternative to counterpoise that is more economical and general, besides yielding a more accurate curve. It may also conceivably justify that extrapolation to the complete basis set limit is, per se, all that is necessary to get a reliable potential function.
使用全组态相互作用和耦合簇方法的计算相结合，通过外推到完全基组极限，得出氦二聚体的真实曲线。通过重新分配基组层次编号，也对全组态相互作用能进行了单独的外推。在任何情况下，都没有采用常见的通过平衡计算来校正基组叠加误差的方法。生成的曲线与最可用的估计值吻合良好，在一个情况下，在最低点的误差在 1 cK（厘开尔文）以内。这证实了我们之前的发现，即这种方法提供了一种替代平衡计算的方法，除了产生更准确的曲线外，它还更加经济和通用。它也可能合理地说明，外推到完全基组极限本身就是获得可靠势能函数所必需的。
