title: Superposition of Fragment Excitations for Excited States of Large Clusters with Application to Helium Clusters.
abstract: We develop a local excited-state method, based on the configuration interaction singles (CIS) wave function, for large atomic and molecular clusters. This method exploits the properties of absolutely localized molecular orbitals (ALMOs), which strictly limits the total number of excitations, and results in formal scaling with the third power of the system size for computing the full spectrum of ALMO-CIS excited states. The derivation of the equations and design of the algorithm are discussed in detail, with particular emphasis on the computational scaling. Clusters containing ∼500 atoms were used in evaluating the scaling, which agrees with the theoretical predictions, and the accuracy of the method is evaluated with respect to standard CIS. A pioneering application to the size dependence of the helium cluster spectrum is also presented for clusters of 25-231 atoms, the largest of which results in the computation of 2310 excited states per sampled cluster geometry.
authors.affiliation: Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Kristina D
authors.initials: KD
authors.lastname: Closser
authors.affiliation: Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Qinghui
authors.initials: Q
authors.lastname: Ge
authors.affiliation: Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California , Berkeley, California 94720, United States.
authors.forename: Yuezhi
authors.initials: Y
authors.lastname: Mao
authors.affiliation: Q-Chem, Inc., 6601 Owens Drive, Suite 105, Pleasanton, California 94588, United States.
authors.forename: Yihan
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Martin
authors.initials: M
authors.lastname: Head-Gordon