{"paper":{"title":"Two Single-Reference Approaches to Singlet Biradicaloid Problems: Complex, Restricted Orbitals and Approximate Spin-Projection Combined With Regularized Orbital-Optimized M{\\o}ller-Plesset Perturbation Theory","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"physics.chem-ph","authors_text":"Joonho Lee, Martin Head-Gordon","submitted_at":"2019-03-27T02:15:40Z","abstract_excerpt":"We present a comprehensive study of two single-reference approaches to singlet biradicaloids. These two approaches are based on the recently developed regularized orbital-optimized M{\\o}ller-Plesset method ($\\kappa$-OOMP2). The first approach is to combine the Yamaguchi's approximate projection (AP) scheme and $\\kappa$-OOMP2 with unrestricted (U) orbitals ($\\kappa$-UOOMP2). By capturing only essential symmetry breaking, $\\kappa$-UOOMP2 can serve as a suitable basis for AP. The second approach is $\\kappa$-OOMP2 with complex, restricted (cR) orbitals ($\\kappa$-cROOMP2). Though its applicability "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1903.11225","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}