TY - JOUR
T1 - An extended multireference study of the electronic states of para-benzyne
AU - Wang, Evan B.
AU - Parish, Carol A.
AU - Lischka, Hans
N1 - Funding Information:
This work was supported to one of the authors (C.P.) by awards from the National Science Foundation (CHE-0211577, CHE-0116435, and CHE-0521063). One of the authors (C.P.) acknowledges the Donors of the American Chemical Society Petroleum Research Fund and the Thomas F. and Kate Miller Jeffress Memorial Trust for partial support of this work. The same author (C.P.) also acknowledges support from the Camille and Henry Dreyfus Foundation through receipt of a Henry Dreyfus Teacher—Scholar award. Another author (E.W.) acknowledges support from the Arnold and Mabel Beckman Foundation through receipt of a Beckman Scholars award and the Howard Hughes Medical Institute through the receipt of an HHMI Summer Fellowship. This work was also supported by the Austrian Science Fund within the framework of the Special Research Program F16 (Advanced Light Sources). We thank Dr. René Kanters for useful discussions and assistance with Fig. . All calculations were carried out at the University of Richmond and computational resources were provided, in part, by the MERCURY supercomputer consortium under NSF Grant No. CHE-0116435 and CHE-0521063.
PY - 2008
Y1 - 2008
N2 - A state-averaged, multireference complete active space (CAS) approach was used for the determination of the vertical excitation energies of valence and Rydberg states of para-benzyne. Orbitals were generated with a 10- and 32-state averaged multiconfigurational self-consistent field approach. Electron correlation was included using multireference configuration interaction with singles and doubles, including the Pople correction for size extensivity, multireference averaged quadratic coupled cluster (MR-AQCC), and MR-AQCC based on linear response theory. There is a very high density of electronic states in this diradical system-there are more than 17 states within 7 eV of the ground state including two 3s Rydberg states. All excitations, except 2 Ag1, are from the π system to the * system. Of the 32 states characterized, 15 were multiconfigurational, including the ground Ag1 state, providing further evidence for the necessity of a multireference approach for p -benzyne. The vertical singlet-triplet splitting was also characterized using a two-state averaged approach. A CAS(2,2) calculation was shown to be inadequate due to interaction with the π orbitals.
AB - A state-averaged, multireference complete active space (CAS) approach was used for the determination of the vertical excitation energies of valence and Rydberg states of para-benzyne. Orbitals were generated with a 10- and 32-state averaged multiconfigurational self-consistent field approach. Electron correlation was included using multireference configuration interaction with singles and doubles, including the Pople correction for size extensivity, multireference averaged quadratic coupled cluster (MR-AQCC), and MR-AQCC based on linear response theory. There is a very high density of electronic states in this diradical system-there are more than 17 states within 7 eV of the ground state including two 3s Rydberg states. All excitations, except 2 Ag1, are from the π system to the * system. Of the 32 states characterized, 15 were multiconfigurational, including the ground Ag1 state, providing further evidence for the necessity of a multireference approach for p -benzyne. The vertical singlet-triplet splitting was also characterized using a two-state averaged approach. A CAS(2,2) calculation was shown to be inadequate due to interaction with the π orbitals.
UR - http://www.scopus.com/inward/record.url?scp=49249113490&partnerID=8YFLogxK
U2 - 10.1063/1.2955744
DO - 10.1063/1.2955744
M3 - Article
C2 - 18681645
AN - SCOPUS:49249113490
SN - 0021-9606
VL - 129
JO - The Journal of Chemical Physics
JF - The Journal of Chemical Physics
IS - 4
M1 - 044306
ER -