{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4e45ca94ffac9e7985c3d3945645440ea5721c57b57a8471fce3e645d5b9e619","created":"2026-10-03T07:17:58Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"dfa20f2cf106240674fcef33b6db8d71f793f2872d3417ea728891b969daeb0f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"chem.excited-states.double-excitation-kernel","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"The standard fast method for excited states, time-dependent density functional theory (TDDFT), describes only states in which one electron is promoted, so states with two electrons promoted are missing. These doubly excited states matter in polyenes, carotenoids and many photochemical pathways.","posed_since":"","precise":"In linear-response TDDFT with a frequency-independent (adiabatic) exchange-correlation kernel $f_{\\mathrm{xc}}$, states of dominant double-excitation character are absent from the spectrum. Construct a frequency-dependent kernel $f_{\\mathrm{xc}}(\\omega)$ applicable to general molecules at cost comparable to hybrid TDDFT that reproduces the 2 1Ag- states of butadiene, hexatriene and octatetraene and the doubly excited states of the QUEST benchmark (a database of near-exact molecular excitation energies) within $0.2\\ \\mathrm{eV}$. An answer is such a kernel with benchmarks, or a proof that no kernel in a stated class can do it.","problem_ref":null,"references":"","settled_by":"Benchmarks of the kernel against near-exact excitation energies for doubly excited states of polyenes and the QUEST set.","status_note":"Dressed kernels introduced in 2004 (Maitra, Zhang, Cave, Burke, J. Chem. Phys., https://doi.org/10.1063/1.1651060) treat isolated doubles; no general-purpose kernel exists.","title":"A practical TDDFT kernel that captures double excitations","topic_ref":"0739ba72a9006ef026985ebb675d97cf7cac60e63cac01f5b754f9a8beff9516"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"0de70e79f9ed74335ecbd5ea621e0f3f90439b8df7d71defdc4b11bcd94639d7","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"bfb8e9f12c5a94119268dbc140734fc3defc74a053927ce5de79c2c30884e7f2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"neyNZ4kAM-I3Gx5ys2nIeOee_sEiW-grYsoAbNDOHuR6BjEvzIyoYR0pgtwIaP0p9WjLmzaFKnobTGDy20w5CQ"},"schema":"pubphys.envelope/1"},"record_hash":"0de70e79f9ed74335ecbd5ea621e0f3f90439b8df7d71defdc4b11bcd94639d7","leaf_index":867}