{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,3]],"date-time":"2026-10-03T05:16:32Z","timestamp":1791004592634,"version":"4.1.0"},"reference-count":39,"publisher":"AIP Publishing","issue":"4","content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,7,28]]},"abstract":"<jats:p>Understanding whether 4f electrons participate directly in lanthanide\u2013lanthanide bonding remains a long-standing question in f-element chemistry. Lanthanide dimers provide the simplest molecular platform for isolating intrinsic metal\u2013metal bonding interactions without ligand-field or oxidation-state complications. Here, we present a fully relativistic multireference investigation of La2, Ce2, and Pr2 to resolve their ground electronic states and elucidate the evolution of bonding across the early lanthanide series. The ground states under spin\u2013orbit coupling are determined to be 0g, 1g, and 2u for La2, Ce2, and Pr2, respectively, with spectroscopic constants in improved agreement with available experimental data. Molecular orbital analysis reveals a common \u03c32\u03c04 inner-core framework, while Ce2 exhibits the highest bond order, consistent with partial multiple-bonding character. Importantly, the results demonstrate that 4f orbitals contribute to metal\u2013metal bonding only through cooperative interaction with energetically accessible 5d orbitals; in the absence of such mixing, the 4f electrons remain essentially nonbonding. These findings provide a unified chemical picture for the onset of f-electron participation in lanthanide bonding and clarify the electronic origin of metal\u2013metal interactions in early lanthanide dimers.<\/jats:p>","DOI":"10.1063\/5.0333281","type":"journal-article","created":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T10:36:03Z","timestamp":1784716563000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":1,"title":["Electronic structure and metal\u2013metal bonding in early lanthanide dimers La2, Ce2, and Pr2"],"prefix":"10.1063","volume":"165","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2214-9610","authenticated-orcid":false,"given":"Huagang","family":"Xiao","sequence":"first","affiliation":[{"name":"College of Physics, Chengdu University of Technology 1 , Chengdu 610059,","place":["China"]},{"name":"Institute of Atomic and Molecular Physics, Sichuan University 2 , Chengdu 610065,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6329-0434","authenticated-orcid":false,"given":"Jianglong","family":"Zhu","sequence":"additional","affiliation":[{"name":"College of Physics, Chengdu University of Technology 1 , Chengdu 610059,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ruijie","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Nuclear Engineering, Seoul National University 3 , 1 Gwanak-ro, Gwanak-gu, Seoul 08826,","place":["South Korea"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xin","family":"Zhou","sequence":"additional","affiliation":[{"name":"Institute of Atomic and Molecular Physics, Sichuan University 2 , Chengdu 610065,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tao","family":"Gao","sequence":"additional","affiliation":[{"name":"Institute of Atomic and Molecular Physics, Sichuan University 2 , Chengdu 610065,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,7,22]]},"reference":[{"key":"2026072206355995100_c1","first-page":"337","volume-title":"The Chemical Bond: Fundamental Aspects of Chemical Bonding","year":"2014"},{"key":"2026072206355995100_c2","volume-title":"Lanthanide and Actinide Chemistry","year":"2024"},{"key":"2026072206355995100_c3","doi-asserted-by":"publisher","first-page":"7891","DOI":"10.1021\/jp035003n","volume":"107","year":"2003","journal-title":"J.\u00a0Phys. 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