Electric field variant ket for the calculation of dynamic polarizabilities. Application to H₂O and N₂

Abstract

The use of a new time-dependent ket, variationally determined as a linear combination of Slater determinants associated with an electric field variant factor, provides an efficient technique for the calculation of dynamic polarizability tensors. Including electron correlation, the method is applied to the evaluation of the frequency-dependent polarizability of H 2 0 and Nz and can be used even when the photon energy is near the excitation energy. With relatively small basis sets, calculated polarizabilities and resonance frequencies are in good agreement with experimental values for H,O but have to be improved for Nz.

Evaluating dynamic multipole polarizabilities and van der Waals dispersion coefficients of two-electron systems with a quantum Monte Carlo calculation: A comparison with someab initiocalculations

“…To do that, we introduce a Markovian diffusion process in configuration space whose transition probability density is closely related to the imaginary-time-dependent Green s function associ- (7) into (10) and comparing with (4). In practice, such averages may be calculated from random walks generated from Eqs.…”

Perturbation expansion of variational principles at arbitrary order

“…A large spectrum of perturbations such as small atomic displacements, electric fields, magnetic fields, small length scale changes, "transmutation" of elements, etc. , eventually time dependent, have been considered, in the framework of widely used ab initio approaches such as the density-functional theory [3 -7] (DFT), Hartree-Fock formalism [8 -14], X approximation [15], multiconfiguration self-consistent field formalism (MCSCF) [9,14,16,17], configuration interaction technique [9,14,17], coupledcluster [9, 14 expansion, and also Moeller-Plesset expansion [9,13, 14 . It is noticeable that a variational principle lies at the heart of most of these approaches.…”

Ab Initio Calculation of the Polarizability for the Ground State XΣ+ and the First Low-Lying Excited States a3Σ+ and A1Σ+ of LiH and NaH

“…In this work, we use the TDGI method, which is a variation-perturbation method with an original expression of the first-order wave function |1〉, including a first degree polynomial function, and taking into account correlation effects as described in detail elsewhere. , In short the construction of the first-order wave function |1〉, which needs in addition to the polynomial function g ( r ), the use of a combination of true spectral states ψ n and a quasi-spectral series φ m , is given by The expansion coefficients are obtained variationally. The polarizability α is then related to the second-order perturbation energy.…”