发表机构
University of Antwerp; University of Montana（安特卫普大学; 蒙大拿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过DFT计算不同尺寸冰团簇上CO、CO2和NH3的吸附能，发现至少需30-40个水分子才能获得可靠结合能，且团簇尺寸与泛函选择同等重要。
AI 中文摘要
冰幔上分子的结合能对于理解分子云中分子复杂性的演化至关重要。结合能通常使用密度泛函理论（DFT）计算，通常在小尺寸的无定形冰团簇或晶体表面上进行。由于这些计算需要对电子结构进行精确描述，通常采用带有色散校正的杂化泛函、基组叠加误差校正和零点能校正。然而，这带来了高昂的计算成本，因此通常考虑较小的冰团簇，其水分子数量往往不超过二十个左右。虽然最近的几项研究探讨了结合能的分布，但很少有研究关注基底尺寸的重要性。我们在此使用六种不同的泛函，对含有10至100个H2O分子的冰团簇进行DFT计算，以量化冰团簇尺寸效应，并将电子贡献与几何贡献分离开来。作为探针分子，我们使用CO、CO2和NH3。这些计算表明，无论使用何种分子和泛函，相互作用能仅从三十到四十个水分子开始收敛。色散能较早趋于平稳，而诱导效应和极化效应则需要更大的团簇才能稳定，尤其是在结构受限（空腔）位点。我们得出结论，至少需要30-40个水分子的冰团簇尺寸才能获得可靠的结合能，这与泛函的选择同等重要。
英文摘要
Binding energies of molecules on ice mantles are important to understand the evolution of molecular complexity in molecular clouds. They are often computed using density functional theory (DFT) calculations, typically on either small amorphous ice clusters or crystalline slabs. Since these calculations require an accurate description of the electronic structure, hybrid functionals with dispersion corrections, basis set superposition error corrections and zero point energy corrections are typically employed. This, however, comes at a high computational cost, so most often small ice clusters are considered, frequently containing no more than twenty water molecules or so. While several recent studies have explored binding energy distributions, the effect of finite cluster size remains insufficiently quantified. To address this gap, we perform DFT calculations using six different functionals, on ice clusters containing 10 to 100 H2O molecules, separating the direct electronic effect of cluster truncation from the geometry-relaxation effects. As probe molecules, we use CO, CO2 and NH3. These calculations demonstrate that, irrespective of the molecule and functional used, interaction energies only start to converge from thirty to forty water molecules onwards. The dispersion energy flattens out earlier, whereas induction and polarisation effects require larger clusters to stabilise, particularly at structurally confined (cavity) sites. We conclude that ice cluster sizes of at least 30-40 water molecules are needed to obtain reliable binding energies, and that cluster size is as important as the choice of the functional.
