How Good Is Koopmans' Approximation? G2(MP2) Study of the Vertical and Adiabatic Ionization Potentials of Some Small Molecules

2002 ◽  
Vol 106 (27) ◽  
pp. 6515-6520 ◽  
Author(s):  
Zvonimir B. Maksić ◽  
Robert Vianello
Keyword(s):  
Small Molecules ◽  
Ionization Potentials

Calculation of Ionization Potentials of Small Molecules:  A Comparative Study of Different Methods

2005 ◽  
Vol 109 (37) ◽  
pp. 8348-8355 ◽  
Author(s):  
Virginie Lemierre ◽  
Anna Chrostowska ◽  
Alain Dargelos ◽  
Henry Chermette
Keyword(s):  
Comparative Study ◽  
Small Molecules ◽  
Ionization Potentials

scholarly journals Fractional Occupation Numbers and Self-Interaction Correction-Scaling Methods with the Fermi-Lowdin Orbital Self-Interaction Correction Approach

2020 ◽  
Author(s):  
Fredy W. Aquino ◽  
Ravindra Shinde ◽  
Bryan Wong
Keyword(s):  
Small Molecules ◽  
Software Package ◽  
Ionization Potentials ◽  
Accuracy Analysis ◽  
Electron Systems ◽  
Occupation Numbers ◽  
Energy Gradient ◽  
Scaling Methods ◽  
Electronic Densities ◽  
Total Energies

We derive an alternate expression for the Fermi-Lowdin Orbital Self-Interaction Correction (FLO-SIC) energy gradient and re-visit how the FLO-SIC methodology can be seen as a constrained unitary transformation acting on canonical Kohn-Sham orbitals. We present a new performance and accuracy analysis of the FLO-SIC approach, which we have recently implemented in the massively-parallelized NWChem quantum chemistry software package. Our FLO-SIC implementation has been tested for the prediction of total energies, atomization energies, and ionization potentials of small molecules and relatively large aromatic systems. The ionization potentials of multi-electron systems are calculated with the adaptation of fractional occupation numbers within FLO-SIC. We also carefully examine the possible improvements of these predictions with various SIC scaling methods based on kinetic energy densities and gradients of electronic densities.

Fractional Occupation Numbers and SIC-Scaling Methods with the Fermi-Lowdin Orbital SIC Approach

2020 ◽  
Author(s):  
Fredy W. Aquino ◽  
Ravindra Shinde ◽  
Bryan Wong
Keyword(s):  
Small Molecules ◽  
Software Package ◽  
Ionization Potentials ◽  
Accuracy Analysis ◽  
Electron Systems ◽  
Occupation Numbers ◽  
Energy Gradient ◽  
Scaling Methods ◽  
Electronic Densities ◽  
Total Energies

We derive an alternate expression for the Fermi-Lowdin Orbital Self-Interaction Correction (FLO-SIC) energy gradient and re-visit how the FLO-SIC methodology can be seen as a constrained unitary transformation acting on canonical Kohn-Sham orbitals. We present a new performance and accuracy analysis of the FLO-SIC approach, which we have recently implemented in the massively-parallelized NWChem quantum chemistry software package. Our FLO-SIC implementation has been tested for the prediction of total energies, atomization energies, and ionization potentials of small molecules and relatively large aromatic systems. The ionization potentials of multi-electron systems are calculated with the adaptation of fractional occupation numbers within FLO-SIC. We also carefully examine the possible improvements of these predictions with various SIC scaling methods based on kinetic energy densities and gradients of electronic densities.

Fractional Occupation Numbers and SIC-Scaling Methods with the Fermi-Lowdin Orbital SIC Approach

2020 ◽  
Author(s):  
Fredy W. Aquino ◽  
Ravindra Shinde ◽  
Bryan Wong
Keyword(s):  
Small Molecules ◽  
Software Package ◽  
Ionization Potentials ◽  
Accuracy Analysis ◽  
Electron Systems ◽  
Occupation Numbers ◽  
Energy Gradient ◽  
Scaling Methods ◽  
Electronic Densities ◽  
Total Energies

We derive an alternate expression for the Fermi-Lowdin Orbital Self-Interaction Correction (FLO-SIC) energy gradient and re-visit how the FLO-SIC methodology can be seen as a constrained unitary transformation acting on canonical Kohn-Sham orbitals. We present a new performance and accuracy analysis of the FLO-SIC approach, which we have recently implemented in the massively-parallelized NWChem quantum chemistry software package. Our FLO-SIC implementation has been tested for the prediction of total energies, atomization energies, and ionization potentials of small molecules and relatively large aromatic systems. The ionization potentials of multi-electron systems are calculated with the adaptation of fractional occupation numbers within FLO-SIC. We also carefully examine the possible improvements of these predictions with various SIC scaling methods based on kinetic energy densities and gradients of electronic densities.

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