Third-order algebraic diagrammatic construction theory for electron attachment and ionization energies: Conventional and Green’s function implementation

Abstract

We present implementation of second-and third-order algebraic diagrammatic construction theory for efficient and accurate computations of molecular electron affinities (EA), ionization potentials (IP), and densities of states (EA-/IP-ADC(n), n = 2, 3). Our work utilizes the non-Dyson formulation of ADC for the singleparticle propagator and reports working equations and benchmark results for the EA-ADC(2) and EA-ADC(3) approximations. We describe two algorithms for solving EA-/IP-ADC equations: (i) conventional algorithm that uses iterative diagonalization techniques to compute low-energy EA, IP, and density of states, and (ii) Green's function algorithm (GF-ADC) that solves a system of linear equations to compute density of states directly for a specified spectral region. To assess accuracy of EA-ADC(2) and EA-ADC(3), we benchmark their performance for a set of atoms, small molecules, and five DNA/RNA nucleobases. As our next step, we demonstrate efficiency of our GF-ADC implementation by computing core-level K-, L-, and M -shell ionization energies of a zinc atom without introducing core-valence separation approximation. Finally, we use EA-and IP-ADC methods to compute band gaps of equally-spaced hydrogen chains H n with n up to 150, providing their estimates near thermodynamic limit. Our results demonstrate that EA-/IP-ADC(n) (n = 2, 3) methods are efficient and accurate alternatives to widely used electronic structure methods for simulations of electron attachment and ionization properties.

Simulating X-ray photoelectron spectra with strong electron correlation using multireference algebraic diagrammatic construction theory

“…106 The CVS-MR-ADC core ionization energies and X-ray photoelectron spectra were compared to the energies and spectra calculated using the single-reference CVS-SR-ADC(2), CVS-SR-ADC(2)-X, and CVS-SR-ADC(3) methods. These methods were implemented in a local version of Pyscf by modifying the implementation of non-Dyson single-reference ADC 104,107 using the same CVS approach as employed in CVS-MR-ADC. Additional calculations using CVS-EOM-CCSD were performed using ORCA.…”

Unified analysis of finite-size error for periodic Hartree-Fock and second order Møller-Plesset perturbation theory

“…From the unified analysis of finite-size errors of the periodic HF theory and the MP2 theory, an immediate question is whether the finite-size errors of higher order Møller-Plesset perturbation theories (MPn) for periodic systems can be analyzed in a similar fashion. This is also a timely question, given the recent resurgence of interests on the third and fourth order perturbation theories in quantum chemistry [2,3,21,34,9]. We expect that the quadrature based analysis of finitesize errors can be carried out to all finite-order perturbation theories, where each energy term in the TDL is a multi-layer integral over Ω * , and its numerical calculation corresponds to a trapezoidal quadrature rule.…”

Recent developments in the PySCF program package

“…Starting from a SCF HF or DFT wavefunction, various many-body methods are available in PYSCF, including Møller-Plesset second-order perturbation theory (MP2), multi-reference perturbation theory (MRPT), 23,24 configuration interaction (CI), [25][26][27][28] coupled cluster (CC), [29][30][31][32][33][34][35][36][37][38] multiconfiguration self-consistent field (MCSCF), 39,40 algebraic diagrammatic construction (ADC) [41][42][43][44][45] and G 0 W 0 46-49 methods. The majority of these capabilities are available for both molecules and crystalline materials.…”

“…An example of this is shown in Figure 7, where the largest CCSD(T) calculation contains 50 electrons and 1500 basis functions. 50 Second-and third-order algebraic diagrammatic construction (ADC) methods are also available in PYSCF for the calculation of molecular electron affinities and ionization potentials [41][42][43][44][45] [EA/IP-ADC(n), n = 2, 3]. These have a lower cost than EA/IP-EOM-CCSD.…”