scholarly journals How to stay out of trouble in RIXS calculations within equation-of-motion coupled-cluster damped response theory? Safe hitchhiking in the excitation manifold by means of core–valence separation

2020 ◽  
Vol 22 (5) ◽  
pp. 2629-2641 ◽  
Author(s):  
Kaushik D. Nanda ◽  
Marta L. Vidal ◽  
Rasmus Faber ◽  
Sonia Coriani ◽  
Anna I. Krylov
Keyword(s):  
Cross Sections ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
X Ray ◽  
X Ray Scattering ◽  
Novel Approach ◽  
Ray Scattering

We present a novel approach with robust convergence of the response equations for computing resonant inelastic X-ray scattering (RIXS) cross sections within the equation-of-motion coupled-cluster (EOM-CC) framework.

scholarly journals How to Stay out of Trouble in RIXS Calculations Within Equation-of-Motion Coupled-Cluster Damped Response Theory? Safe Hitchhiking in the Excitation Manifold by Means of Core-Valence Separation

2019 ◽  
Author(s):  
Kaushik Nanda ◽  
Marta L. Vidal ◽  
Rasmus Faber ◽  
Sonia Coriani ◽  
Anna Krylov
Keyword(s):  
Cross Sections ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
Excitation Energies ◽  
X Ray ◽  
X Ray Scattering ◽  
Novel Approach ◽  
Response Equation ◽  
Divergent Behavior

<div>We present a novel approach for computing resonant inelastic X-ray scattering (RIXS) cross sections within the equation-of-motion coupled-cluster (EOM-CC) framework. The approach is based on recasting the sum-over-state expressions for RIXS moments into a compact form by using damped response theory. Damped response formalism allows one to circumvent problems of divergent behavior of the response equation in the resonant regime. However, the convergence of response equations in the X-ray frequency range is often erratic due to the resonant nature of the virtual core-excited states embedded in the valence ionization continuum. We demonstrate that this problematic behavior can be avoided by extending the core-valence separation (CVS) scheme, which decouples the valence-occupied and core-occupied excitation manifolds, into the response domain. The accuracy of the CVS-enabled damped response theory, implemented within the EOM-EE-CCSD (EOM-CC for excitation energies with single and double excitations) framework, is assessed by comparison against damped EOM-EE-CCSD response calculations. The capabilities of the new approach are illustrated by calculations of RIXS cross sections for benzene and benzene radical cation.</div>

scholarly journals How to Stay out of Trouble in RIXS Calculations Within the Equation-of-Motion Coupled-Cluster Damped Response Theory Framework? Safe Hitchhiking in the Excitation Manifold by Means of Core-Valence Separation

2019 ◽  
Author(s):  
Kaushik Nanda ◽  
Marta L. Vidal ◽  
Rasmus Faber ◽  
Sonia Coriani ◽  
Anna Krylov
Keyword(s):  
Cross Sections ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
Excitation Energies ◽  
X Ray ◽  
X Ray Scattering ◽  
Novel Approach ◽  
Response Equation ◽  
Divergent Behavior

<div>We present a novel approach for computing resonant inelastic X-ray scattering (RIXS) cross sections within the equation-of-motion coupled-cluster (EOM-CC) framework. The approach is based on recasting the sum-over-state expressions for RIXS moments into a compact form by using damped response theory. Damped response formalism allows one to circumvent problems of divergent behavior of the response equation in the resonant regime. However, the convergence of response equations in the X-ray frequency range is often erratic due to the resonant nature of the virtual core-excited states embedded in the valence ionization continuum. We demonstrate that this problematic behavior can be avoided by extending the core-valence separation (CVS) scheme, which decouples the valence-occupied and core-occupied excitation manifolds, into the response domain. The accuracy of the CVS-enabled damped response theory, implemented within the EOM-EE-CCSD (EOM-CC for excitation energies with single and double excitations) framework, is assessed by comparison against damped EOM-EE-CCSD response calculations. The capabilities of the new approach are illustrated by calculations of RIXS cross sections for benzene and benzene radical cation.</div>

scholarly journals How to Stay out of Trouble in RIXS Calculations Within Equation-of-Motion Coupled-Cluster Damped Response Theory? Safe Hitchhiking in the Excitation Manifold by Means of Core-Valence Separation

2019 ◽  
Author(s):  
Kaushik Nanda ◽  
Marta L. Vidal ◽  
Rasmus Faber ◽  
Sonia Coriani ◽  
Anna Krylov
Keyword(s):  
Cross Sections ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
Excitation Energies ◽  
X Ray ◽  
X Ray Scattering ◽  
Novel Approach ◽  
Response Equation ◽  
Divergent Behavior

<div>We present a novel approach for computing resonant inelastic X-ray scattering (RIXS) cross sections within the equation-of-motion coupled-cluster (EOM-CC) framework. The approach is based on recasting the sum-over-state expressions for RIXS moments into a compact form by using damped response theory. Damped response formalism allows one to circumvent problems of divergent behavior of the response equation in the resonant regime. However, the convergence of response equations in the X-ray frequency range is often erratic due to the resonant nature of the virtual core-excited states embedded in the valence ionization continuum. We demonstrate that this problematic behavior can be avoided by extending the core-valence separation (CVS) scheme, which decouples the valence-occupied and core-occupied excitation manifolds, into the response domain. The accuracy of the CVS-enabled damped response theory, implemented within the EOM-EE-CCSD (EOM-CC for excitation energies with single and double excitations) framework, is assessed by comparison against damped EOM-EE-CCSD response calculations. The capabilities of the new approach are illustrated by calculations of RIXS cross sections for benzene and benzene radical cation.</div>

scholarly journals Resonant Inelastic X-Ray Scattering and Non Resonant X-ray Emission Spectra from Coupled-Cluster (Damped) Response Theory

2018 ◽  
Author(s):  
Rasmus Faber ◽  
Sonia Coriani
Keyword(s):  
Gas Phase ◽  
Emission Spectra ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
Simple Scheme ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Spectra ◽  
Ray Scattering

A coupled cluster protocol rooted in damped response theory is presented for computing Resonant Inelastic X-Ray Scattering spectra of molecules in gas-phase. Working equations are reported for both linear (i.e., equation-of-motion) and non-linear<br>parametrizations of the coupled-cluster wavefunction response. A simple scheme to<br>compute non-resonant X-ray emission spectra is also proposed. Illustrative results are<br>presented for water.

scholarly journals Resonant Inelastic X-Ray Scattering and Non Resonant X-ray Emission Spectra from Coupled-Cluster (Damped) Response Theory

2018 ◽  
Author(s):  
Rasmus Faber ◽  
Sonia Coriani
Keyword(s):  
Gas Phase ◽  
Emission Spectra ◽  
Equation Of Motion ◽  
Coupled Cluster ◽  
Response Theory ◽  
Simple Scheme ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Spectra ◽  
Ray Scattering

A coupled cluster protocol rooted in damped response theory is presented for computing Resonant Inelastic X-Ray Scattering spectra of molecules in gas-phase. Working equations are reported for both linear (i.e., equation-of-motion) and non-linear<br>parametrizations of the coupled-cluster wavefunction response. A simple scheme to<br>compute non-resonant X-ray emission spectra is also proposed. Illustrative results are<br>presented for water.

Leather Structure Determination by Small-Angle X-ray Scattering (SAXS): Cross Sections of Ovine and Bovine Leather

2010 ◽  
Vol 58 (9) ◽  
pp. 5286-5291 ◽  
Author(s):  
Melissa M. Basil-Jones ◽  
Richard L. Edmonds ◽  
Timothy F. Allsop ◽  
Sue M. Cooper ◽  
Geoff Holmes ◽  
...  
Keyword(s):  
Cross Sections ◽  
Structure Determination ◽  
Small Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering
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