Thermochemical Trends in Carbon Chain Molecules HC2kH/HC2k-1H (k = 1–6) Studied by Explicitly Correlated CCSD(T)-F12b Composite Methods
| Autor: | Chow-Shing Lam, Kai-Chung Lau |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
chemistry.chemical_classification
010304 chemical physics Chemistry Scalar (mathematics) Extrapolation 010402 general chemistry 01 natural sciences Molecular physics Standard enthalpy of formation 0104 chemical sciences Interstellar medium 0103 physical sciences Molecule Compounds of carbon Physics::Chemical Physics Physical and Theoretical Chemistry Ionization energy Relativistic quantum chemistry |
| Zdroj: | The Journal of Physical Chemistry A. 125:5385-5396 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.1c03428 |
| Popis: | We present a composite procedure based on explicitly correlated CCSD(T)-F12 calculations for accurate energetic predictions for carbon chain molecules HCnH encompassing both the even (HC2kH) and odd series (HC2k-1H), with the shorter members playing a key role in the evolution of cosmic carbon compounds in both circumstellar envelopes and interstellar medium. This approach considers the contributions of core-valence correlation, scalar relativistic effect, spin-orbit coupling, and zero-point vibrational energy in an additive manner. The computed ionization energies demonstrate outstanding agreement (±0.07 eV) up to a chain size of k = 6 and the literature heats of formation for k ≤ 2 are reproduced with "chemical accuracy" of 1 kcal mol-1. Among the various corrections included, the importance of core-valence correlation effect has been highlighted in the thermochemical calculations for carbon chain growth. The thermochemical trend toward infinite length is also highlighted by extrapolation of ionization energy and triplet-singlet splitting at the CCSD(T) level for k up to 15. The correlation between the end-group effect and the even-odd parity effect observed for HCnH chains has been established with the aid of intrinsic bond orbital localization. |
| Databáze: | OpenAIRE |
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