scholarly journals Feshbach–Fano approach for calculation of Auger decay rates using equation-of-motion coupled-cluster wave functions. I. Theory and implementation

2021 ◽  
Vol 154 (8) ◽  
pp. 084124 ◽  
Author(s):  
Wojciech Skomorowski ◽  
Anna I. Krylov
Keyword(s):  
Equation Of Motion ◽  
Decay Rates ◽  
Wave Functions ◽  
Coupled Cluster ◽  
Auger Decay

scholarly journals Feshbach-Fano Approach for Calculation of Auger Decay Rates Using Equation-of-Motion Coupled-Cluster Wave Functions: Theory and Implementation

2020 ◽  
Author(s):  
Wojciech Skomorowski ◽  
Anna Krylov
Keyword(s):  
Electronic State ◽  
Equation Of Motion ◽  
General Purpose ◽  
Decay Rates ◽  
Coupled Cluster ◽  
Projection Technique ◽  
Auger Process ◽  
Auger Decay ◽  
Outgoing Electron ◽  
General Purpose Software

<p>We present a novel methodology to calculate Auger decay rates based on equation-of -motion coupled-cluster singles and doubles (EOM-CCSD) wave function, combined with a simplified continuum orbital describing the outgoing electron. In our approach the Auger process is considered as an autoionization of a resonant electronic state, which can be described with Feshbach-Fano projection technique in order to distill the resonance parameters. To this end, we employ core-valence separation (CVS) scheme as a method to extract the bound part of the decaying many-electronic state. Main advantages of our methodology include (1) flexible EOM-CCSD ansatz enabling to describe various electronic states, (2) simple, yet universal computational setup, (3) fast computations due to fully analytical evaluation of all mixed bound-continuum two-electron integrals, and (4) implementation in general-purpose software package for quantum-chemical calculations.</p>

scholarly journals Feshbach-Fano Approach for Calculation of Auger Decay Rates Using Equation-of-Motion Coupled-Cluster Wave Functions: Numerical Examples and Benchmarks

2020 ◽  
Author(s):  
Wojciech Skomorowski ◽  
Anna Krylov
Keyword(s):  
Auger Electron ◽  
Equation Of Motion ◽  
Decay Rates ◽  
Coupled Cluster ◽  
Numerical Illustration ◽  
Auger Decay ◽  
Benchmark Tests ◽  
Analytical Approximations ◽  
Auger Spectra ◽  
Auger Electron Spectra

<p>This manuscript is concerned with numerical illustration of the theoretical framework for computing Auger decay rates based on the Feshbach-Fano approach and the equation-of-motion coupled-cluster ansatz, augmented with core-valence separation scheme. We consider two analytical approximations to the continuum orbital describing the Auger electron: a plane wave and a Coulomb wave with an effective charge. Theoretical Auger electron spectra are presented for benchmark systems (Ne, H<sub>2</sub>O, CH<sub>4</sub> and CO<sub>2</sub>) and compared with available experimental spectra. Results of the presented benchmark tests show that the proposed computational scheme provides reliable <i>ab initio</i> preditions of the Auger spectra. The reliability, cost-efficiency, and robust computational setup of this methodology offer advantages in applications to a large variety of systems. </p>

scholarly journals Feshbach-Fano Approach for Calculation of Auger Decay Rates Using Equation-of-Motion Coupled-Cluster Wave Functions: Numerical Examples and Benchmarks

2020 ◽  
Author(s):  
Wojciech Skomorowski ◽  
Anna Krylov
Keyword(s):  
Auger Electron ◽  
Equation Of Motion ◽  
Decay Rates ◽  
Coupled Cluster ◽  
Numerical Illustration ◽  
Auger Decay ◽  
Benchmark Tests ◽  
Analytical Approximations ◽  
Auger Spectra ◽  
Auger Electron Spectra

<p>This manuscript is concerned with numerical illustration of the theoretical framework for computing Auger decay rates based on the Feshbach-Fano approach and the equation-of-motion coupled-cluster ansatz, augmented with core-valence separation scheme. We consider two analytical approximations to the continuum orbital describing the Auger electron: a plane wave and a Coulomb wave with an effective charge. Theoretical Auger electron spectra are presented for benchmark systems (Ne, H<sub>2</sub>O, CH<sub>4</sub> and CO<sub>2</sub>) and compared with available experimental spectra. Results of the presented benchmark tests show that the proposed computational scheme provides reliable <i>ab initio</i> preditions of the Auger spectra. The reliability, cost-efficiency, and robust computational setup of this methodology offer advantages in applications to a large variety of systems. </p>

scholarly journals Feshbach-Fano Approach for Calculation of Auger Decay Rates Using Equation-of-Motion Coupled-Cluster Wave Functions: Theory and Implementation

2020 ◽  
Author(s):  
Wojciech Skomorowski ◽  
Anna Krylov
Keyword(s):  
Electronic State ◽  
Equation Of Motion ◽  
General Purpose ◽  
Decay Rates ◽  
Coupled Cluster ◽  
Projection Technique ◽  
Auger Process ◽  
Auger Decay ◽  
Outgoing Electron ◽  
General Purpose Software

<p>We present a novel methodology to calculate Auger decay rates based on equation-of -motion coupled-cluster singles and doubles (EOM-CCSD) wave function, combined with a simplified continuum orbital describing the outgoing electron. In our approach the Auger process is considered as an autoionization of a resonant electronic state, which can be described with Feshbach-Fano projection technique in order to distill the resonance parameters. To this end, we employ core-valence separation (CVS) scheme as a method to extract the bound part of the decaying many-electronic state. Main advantages of our methodology include (1) flexible EOM-CCSD ansatz enabling to describe various electronic states, (2) simple, yet universal computational setup, (3) fast computations due to fully analytical evaluation of all mixed bound-continuum two-electron integrals, and (4) implementation in general-purpose software package for quantum-chemical calculations.</p>

scholarly journals General Framework for Calculating Spin–orbit Couplings Using Spinless One-Particle Density Matrices: Theory and Application to the Equation-of-Motion Coupled-Cluster Wave Functions

2019 ◽  
Author(s):  
Pavel Pokhilko ◽  
Evgeny Epifanovsky ◽  
Anna I. Krylov
Keyword(s):  
Degrees Of Freedom ◽  
Particle Density ◽  
Mean Field ◽  
Transition Density ◽  
Open Shell ◽  
Equation Of Motion ◽  
Wave Functions ◽  
Coupled Cluster ◽  
Spin Orbit ◽  
Matrix Elements

Standard implementations of non-relativistic excited-state calculations compute only one component of spin multiplets (i.e., Ms =0 triplets), however, matrix elements for all components are necessary for calculations of experimentally relevant spin-dependent quantities. To circumvent explicit calculations of all multiplet components, we employ Wigner–Eckart’s theorem. Applied to a reduced one-particle transition density matrix computed for a single multiplet component, Wigner–Eckart’s theorem generates all other spin–orbit matrix elements. In addition to computational efficiency, this approach also resolves the phase issue arising within Born–Oppenheimer’s separation of nuclear and electronic degrees of freedom. A general formalism and its application to the calculations of spin–orbit couplings using equation-of-motion coupled-cluster wave functions is presented. The two-electron contributions are included via the mean-field spin–orbit treatment. Intrinsic issues of constructing spin–orbit mean-field operators for open-shell references are discussed and a resolution is proposed. The method is benchmarked by using several radicals and diradicals. The merits of the approach are illustrated by a calculation of the barrier for spin inversion in a high-spin tris(pyrrolylmethyl)amine Fe(II) complex.

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