发表机构
School of Physics and Astronomy, University of Leeds; Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción（利兹大学物理与天文学院; 康塞普西翁大学化学科学学院物理化学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究计算了12种吸附质在CO₂团簇上的结合能，明确其结合强度与氢键供体-受体特性相关，发现CO₂有限的氢键能力可促进混合冰分离，并给出不同吸附质的脱附温度。
AI 中文摘要
二氧化碳（CO₂）是最丰富的星际冰之一，已被詹姆斯·韦布空间望远镜（JWST）在富水混合物及纯CO₂环境中观测到。天体化学模型采用在水冰上测得的结合能（BE），因为CO₂冰的结合能数据很少。我们使用经CCSD(T)/CBS（外推至完全基组极限的耦合簇方法）校准的DFT，计算了12种吸附质（N₂、CH₄、HCl、C₂H₂、H₂S、HF、HCN、H₂CO、HCOOH、HNC、CH₃OH、H₂O）在含2至5个分子的CO₂团簇上的结合能分布。结合强度取决于吸附质是否需要表面提供氢键（H键）：CO₂可作为H键受体但无法作为供体，与Ahmad等人（2026）研究中与水冰对比的6种物种相比，它们在CO₂上的结合更弱。CO₂与水冰上的结合能比值，H₂CO为0.66、H₂O为0.75、CH₃OH为0.87、HCOOH为0.89、C₂H₂为0.92。据预测，甲醛在富CO₂冰上的脱附温度约为57 K，而在富水冰上为85 K，可能对冷气相H₂CO有贡献。尽管部分物种的平均结合能随团簇大小变化，但差异可追溯至局部结合相互作用，且这种相互作用在更大的冰模型中仍可能重要。不同位点间结合能差异超500 K，脱附峰范围为CH₄的11 K至HCOOH的132 K。CO₂有限的H键结合能力可能促进H₂O:CO₂混合冰分离为富CO₂区域。
英文摘要
Carbon dioxide (CO$_2$) is among the most abundant interstellar ices and has been observed by JWST in water-rich mixtures and pure CO$_2$ environments. Astrochemical models adopt binding energies (BEs) measured on water ice because few BEs are available for CO$_2$ ice. We calculate BE distributions for twelve adsorbates (N$_2$, CH$_4$, HCl, C$_2$H$_2$, H$_2$S, HF, HCN, H$_2$CO, HCOOH, HNC, CH$_3$OH, H$_2$O) on CO$_2$ clusters containing two to five molecules using DFT calibrated against CCSD(T)/CBS, a coupled-cluster treatment extrapolated to the complete-basis-set limit. Binding strength depends on whether the adsorbate requires the surface to donate a hydrogen bond (H-bond). CO$_2$ can accept an H-bond but cannot donate one, and all six species compared with water ice from Ahmad et al. (2026) bind more weakly on CO$_2$. The ratio of the BE on CO$_2$ to water ice ranges from 0.66 for H$_2$CO and 0.75 for H$_2$O to 0.87 for CH$_3$OH, 0.89 for HCOOH and 0.92 for C$_2$H$_2$. Formaldehyde is predicted to desorb near 57 K from CO$_2$-rich ice, compared with 85 K from water-rich ice, and could contribute to cold gas-phase H$_2$CO. Although the mean binding energies are changing with cluster size for several species, the differences can be traced to local binding interactions likely to remain important in larger ice models. The BEs vary by more than 500 K between sites, while the desorption peaks range from 11 K for CH$_4$ to 132 K for HCOOH. The limited H-bonding capacity of CO$_2$ may favour separation of mixed H$_2$O:CO$_2$ ice into CO$_2$-rich domains.
CommentsIn revision at The Astrophysical Journal
