Implementation of the infinite-range exterior complex scaling to the time-dependent complete-active-space self-consistent-field method

Abstract

We present a numerical implementation of the infinite-range exterior complex scaling (irECS) [Phys. Rev. A 81, 053845 (2010)] as an efficient absorbing boundary to the time-dependent complete-active-space self-consistent field (TD-CASSCF) method [Phys. Rev. A 94, 023405 (2016)] for multielectron atoms subject to an intense laser pulse. We introduce Gauss-Laguerre-Radau quadrature points to construct discrete variable representation basis functions in the last radial finite element extending to infinity. This implementation is applied to strong-field ionization and high-harmonic generation in He, Be, and Ne atoms. It efficiently prevents unphysical reflection of photoelectron wave packets at the simulation boundary, enabling accurate simulations with substantially reduced computational cost, even under significant (≈ 50%) double ionization. For the case of a simulation of high-harmonic generation from Ne, for example, 80% cost reduction is achieved, compared to a mask-function absorption boundary.

Communication: Time-dependent optimized coupled-cluster method for multielectron dynamics

“…25,28 These codes share the same implementation for the basis-independent procedures [Eqs. (13), (14), (17)- (19), and (21)- (23)].…”

“…not occupied in the reference (particle). These methods achieve a polynomial, instead of factorial, cost scaling, and state-of-the-art real-space implementations 23,[25][26][27][28] have proved their great utility; however, truncated-CI-based methods share a general drawback of not being size extensive. 29 Therefore, one naturally seeks an alternative to Eq.…”

Application of the time-dependent surface flux method to the time-dependent multiconfiguration self-consistent-field method

“…(28) below], wave functions and their spatial derivative only on the surface |r| = R s are required to solve Eq. (18). Hence, it is no longer needed to keep the whole wave function and allowed to use an absorbing boundary, which leads to a significant computational cost reduction.…”

“…Although the time-dependent Schrödinger equation (TDSE) provides a rigorous theoretical framework to investigate electron dynamics, solving it for multielectron systems poses a major challenge. To simulate multielectron dynamics in intense laser fields, the timedependent multiconfiguration self-consistent field (TD-MCSCF) methods have been developed [3][4][5][6][7][8][9][10][11][12] which express the total wave function as a superposition,…”

“…They contain an additional term compared with the single-electron case. While we use the infinite-range exterior complex scaling (irECS) [17,18] as an efficient absorbing boundary, the present tSURFF implementation also supports other absorption boundaries such as mask functions and complex absorbing potentials. We achieve highly accurate calculations of angle-resolved PES with considerably reduced computational costs.…”