{"doi":"10.1002/qua.560420208","title":"Electronic states and nature of the chemical bond in the molecule CrC by all‐electron ab initio calculations","abstract":"<jats:title>Abstract</jats:title><jats:p>All‐electron ab initio Hartree–Fock (<jats:sc>HF</jats:sc>), valence configuration interaction (<jats:sc>CI</jats:sc>), and multiconfiguration self‐consistent‐field (<jats:sc>CASSCF</jats:sc>) calculations have been applied to investigate the electronic states of the CrC molecule. The molecule is predicted as having four low‐lying electronic states, <jats:sup>3</jats:sup>∑<jats:sup>−</jats:sup>, <jats:sup>5</jats:sup>∑<jats:sup>−</jats:sup>, <jats:sup>7</jats:sup>∑<jats:sup>−</jats:sup>, and <jats:sup>9</jats:sup>∑<jats:sup>−</jats:sup>, separated by an energy gap of 0.55 eV from the next higher‐lying state, <jats:sup>1</jats:sup>∑<jats:sup>−</jats:sup>, which is followed by the states <jats:sup>5</jats:sup>Π and <jats:sup>7</jats:sup>Π. The four lowest‐lying electronic states are due to the coupling of the angular momenta of the <jats:sup>6</jats:sup><jats:italic>S</jats:italic><jats:sub><jats:italic>g</jats:italic></jats:sub> Cr<jats:sup>+</jats:sup> ion with those of the <jats:sup>4</jats:sup><jats:italic>S</jats:italic><jats:sub><jats:italic>u</jats:italic></jats:sub> C<jats:sup>−</jats:sup> anion. The chemical bond in the <jats:sup>3</jats:sup>∑<jats:sup>−</jats:sup> ground state can be viewed as a quadruple bond composed of two σ and two π bonds. One σ bond is due to the formation of a molecular orbital that is doubly occupied. The remaining bonds, i.e., one σ and two π bonds, arise from valence‐bond couplings. The π bonds originate from the valence‐bond couplings of the electrons in the C 2<jats:italic>p</jats:italic>π orbitals with those in the Cr 3<jats:italic>d</jats:italic>π orbitals. The σ bond originates from the valence‐bond coupling of the C 2<jats:italic>p</jats:italic>σ electron with an electron in the Cr 4<jats:italic>s</jats:italic>, 4<jats:italic>p</jats:italic> hybrid that is polarized away from the C atom.</jats:p>","journal":"International Journal of Quantum Chemistry","year":1992,"id":17429,"datarank":1.9763745994065842,"base_score":3.332204510175204,"endowment":3.332204510175204,"self_citation_contribution":0.49983067652628066,"citation_network_contribution":1.4765439228803037,"self_endowment_contribution":0.49983067652628066,"citer_contribution":1.4765439228803037,"corpus_percentile":null,"corpus_rank":null,"citation_count":27,"citer_count":25,"citers_with_citation_signal":23,"citers_with_endowment":23,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":124744,"name":"Karl A. Gingerich","orcid":null,"position":1,"is_corresponding":false},{"id":124743,"name":"Irene Shim","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":3.332204510175204,"endowment":3.332204510175204,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"24259432","pmcid":null,"openalex_id":"https://openalex.org/W2044772721","authors":[],"funders":[],"total_grants":0,"fwci":0.2356,"citation_percentile":0.48928761,"influential_citations":0,"citation_trend":[{"year":2013,"count":1},{"year":2022,"count":1},{"year":2025,"count":1}],"oa_status":"closed","license":"http://onlinelibrary.wiley.com/termsAndConditions#vor","oa_locations":[{"url":"https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqua.560420208","host_type":"publisher"},{"url":"https://onlinelibrary.wiley.com/doi/pdf/10.1002/qua.560420208","host_type":"publisher"},{"url":"https://doi.org/10.1002/qua.560420208","host_type":"journal"}],"fields_of_study":["Advanced Chemical Physics Studies","Inorganic Chemistry and Materials","Molecular Junctions and Nanostructures","Chemistry"],"mesh_terms":[],"keywords":["Chemistry","Three-center two-electron bond","Valence bond theory","Generalized valence bond","Chemical bond","Single bond","Ab initio","Atomic physics","Sextuple bond","Valence (chemistry)","Atomic orbital","Electron configuration","Molecular orbital","Molecule","Bond order","Valence electron","Quadruple bond","Bond energy","Modern valence bond theory","Orbital hybridisation","Bond length","Ion","Electron","Physics","Group (periodic table)","Quantum mechanics"],"sdg_mappings":[{"sdg_number":0,"sdg_label":"Affordable and clean energy"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-02T18:51:38.938595Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}