European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*-FBK), via Sommarive 18, I-38123 Trento, Italy.
Faculty of Chemistry, Nicolaus Copernicus University in Torun, Gagarina 7, PL-87-100 Torun, Poland.
J Chem Phys. 2017 Feb 7;146(5):054304. doi: 10.1063/1.4974993.
We use a new high-accuracy all-dimensional potential to compute the cross second virial coefficient B(T) between molecular hydrogen and carbon monoxide. The path-integral method is used to fully account for quantum effects. Values are calculated from 10 K to 2000 K and the uncertainty of the potential is propagated into uncertainties of B. Our calculated B(T) are in excellent agreement with most of the limited experimental data available, but cover a much wider range of temperatures and have lower uncertainties. Similar to recently reported findings from scattering calculations, we find that the reduced-dimensionality potential obtained by averaging over the rovibrational motion of the monomers gives results that are a good approximation to those obtained when flexibility is fully taken into account. Also, the four-dimensional approximation with monomers taken at their vibrationally averaged bond lengths works well. This finding is important, since full-dimensional potentials are difficult to develop even for triatomic monomers and are not currently possible to obtain for larger molecules. Likewise, most types of accurate quantum mechanical calculations, e.g., spectral or scattering, are severely limited in the number of dimensions that can be handled.
我们使用新的高精度全维势能来计算分子氢和一氧化碳之间的交叉第二维里系数 B(T)。路径积分方法被用来充分考虑量子效应。计算值从 10 K 到 2000 K，并且将势能的不确定性传播到 B 的不确定性中。我们计算的 B(T)与大多数现有的有限实验数据非常吻合，但涵盖了更广泛的温度范围，并且具有更低的不确定性。与最近报道的散射计算结果相似，我们发现通过对单体的转动和振动运动进行平均得到的降维势能给出的结果与充分考虑灵活性时得到的结果非常接近。此外，采用振动平均键长的单体的四元近似也能很好地工作。这一发现非常重要，因为即使对于三原子单体，全维势能也很难开发，而且目前还不可能获得更大分子的全维势能。同样，大多数类型的精确量子力学计算，例如光谱或散射，在能够处理的维度数量上受到严重限制。
