Multi-reference approach to the computation of double core-hole spectra

Abstract

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Disentangling the resonant Auger spectra of ozone: overlapping core-hole states and core-excited state dynamics

“…At its ground state the ozone molecule belongs to the C 2v point group symmetry with experimentally determined structural parameters 80 Similar to what we did in previous studies, 52,66 to facilitate the application and analysis of the OCA projection on symmetry equivalent atomic sites, we have reduced the point group symmetry from C 2v to C s , and localized the core orbitals by applying a Cholesky localization procedure. 81 Moreover, we find it particularly convenient to use C s symmetry because we calculate Auger spectra along a (dissociative) molecular dynamics trajectory, where C s symmetry can always be applied.…”

Multireference Approach to Normal and Resonant Auger Spectra Based on the One-Center Approximation

“…To facilitate the application of the OCA in this molecular system with two equivalent atoms, we have reduced the point group symmetry to C 2 v and localized the core orbitals applying a Cholesky localization procedure, 95 similar to what we recently did to compute double-core-hole spectra. 75 Alternatively, one could have localized the core orbitals using the Boys 109 or the Pipek–Mezey 110 methods. However, this would imply lowering the point group symmetry to C 1 , which is a path we find less attractive, as point group symmetry reduces the computational effort and facilitates the analysis of the results.…”

“…The RAS2 contains all the occupied orbitals , 2σ 2 , 3σ 2 , 1π 4 ) plus the 4σ and 2π virtual orbitals. To facilitate the application of the OCA in this molecular system with two equivalent atoms, we have reduced the point group symmetry to C 2 v and localized the core orbitals applying a Cholesky localization procedure, similar to what we recently did to compute double-core-hole spectra . Alternatively, one could have localized the core orbitals using the Boys or the Pipek–Mezey methods.…”

“… 72 , 73 In our implementation of eq 9 , the annihilation operator acts on the space of the molecular orbitals of the final state wave function, , and the annihilation operators act on the space of molecular orbitals of the initial state wave function, . We note in passing that matrix elements analogous to those of eq 9 have been recently implemented in OpenMolcas by Tenorio et al 75 for the evaluation of double core–hole shakeup spectra.…”

“…The spin-adapted Auger matrix elements R KI ; qsr (also called the two-particle Dyson matrix), can be conveniently computed using a biorthonormalized set of molecular orbitals within the Restricted Active Space–State Interaction (RASSI) method, , and we have implemented them in a locally modified version of the OpenMolcas program package. , In our implementation of eq , the annihilation operator acts on the space of the molecular orbitals of the final state wave function, , and the annihilation operators act on the space of molecular orbitals of the initial state wave function, . We note in passing that matrix elements analogous to those of eq have been recently implemented in OpenMolcas by Tenorio et al for the evaluation of double core–hole shakeup spectra.…”