An efficient combination of computational techniques for investigating electronic resonance states in molecules

Abstract

Articles you may be interested inThe complex scaled multiconfigurational time-dependent Hartree-Fock method for studying resonant states: Application to the 2s 2 He Feshbach resonance J. Chem. Phys. 140, 094305 (2014); 10.1063/1.4867059Continuum remover-complex absorbing potential: Efficient removal of the nonphysical stabilization points Accurately solving the electronic Schrödinger equation of atoms and molecules using explicitly correlated (r 12 -)MR-CI. II. Ground-state energies of first-row atoms and positive atomic ions Calculating electronic resonance states in molecules is a serious challenge to theory, because the treatment of both the scattering and the many-electron problem is a formidable task. A very promising approach, known as CAP/CI, consists of the combination of a complex absorbing potential with the method of configuration interaction. In this paper we propose the combination of three distinct computational techniques in order to boost the performance of CAP/CI. A complex absorbing potential that can be adjusted flexibly to the geometry of the molecular scattering target is presented and its representation in a Gaussian basis set is discussed. To handle the large-scale complex symmetric eigenvalue problem arising in CAP/CI, a subspace projection method is employed and its validity is shown. We advocate the use of parallel filter diagonalization for calculating the eigenvectors required in the projection step. The proposed techniques are applied to determine the lifetime of an autoionizing, inner-valence excited state of Ne 2 ϩ .

Time-resolved studies of interatomic Coulombic decay

“…The error is purely statistical and the value gives an upper limit for the lifetime. This measured lifetime cannot be compared directly to computed ICD rates at a fixed internuclear distance or at a range of distances [20,57,22,58]. Instead, quantum mechanical calculations including the nuclear wave packet dynamics in the intermediate states must be performed, using the computational technique of [59].…”

Analytically continued Fock space multi-reference coupled-cluster theory: Application to the shape resonance

“…Recent years have witnessed advances in ab initio quantum chemical techniques using the analytical continuation methods for probing the electronic resonances in atoms and molecules [1][2][3][4][5][6][7][8][9][10]. The advantage of analytical continuation of the Hamiltonian in the complex plane giving the direct access to the resonances parameters is that they can be represented by using L 2 wavefunction [1].…”

“…The associated complex eigen-value then gives the position and width of the resonance or the auto-ionizing state. The CAP procedure is minimally invasive in the sense that neither the internal structure of the physical Hamiltonian is affected nor is there any need to use other basis sets than usual real Gaussians and thus many existing electronic structure calculations for bound states of molecule can adapt to the resonance [3].…”

“…The accuracy of the effective oneparticle based approximations in the case of an electron scattering resonance depends on the extent to which the electron correlation is important in the description of particular states. CAP potentials have been applied to the molecular resonances in the context of configuration interaction [CI] [6] and electron propagator theories [3,4] and coupled-cluster based methods [7][8][9]. In these calculations, the resonance energies and width are calculated from the difference between the ground state total energies of the [N ± 1] and the neutral target.…”

Ab initio calculation of interatomic decay rates of excited doubly ionized states in clusters

“…The method proved to be superior to the Wigner-Weisskopf method [17] since effects like orbital relaxation, intra-atomic correlation, and channel coupling are fully taken into account. Furthermore, size-consistency (i.e., energy separability with respect to dissociation of a large system into multiple non-interacting fragments) and compactness of the matrices to diagonalize resulting from comparatively small explicit configuration space [18,19] makes the ADC-based approach applicable even to large atomic or molecular clusters, for which alter-native methods such as CAP-CI [20,21] are not suitable. Still, in applications of the present method to extended systems attention has to paid to the fact that size-consistency in the dissociation limit need not necessarily ensure the proper size-intensive or size-extensive scaling of physical quantities.…”