Configuration interaction study of the electronic spectrum of methinophosphide, HCP

1990 ◽  
Vol 68 (6) ◽  
pp. 499-507 ◽  
Author(s):  
S. P. Karna ◽  
P. J. Bruna ◽  
F. Grein
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Basis Sets ◽  
Spectroscopic Constants ◽  
Stable States ◽  
Excitation Energies ◽  
Doubly Excited States ◽  
Plane Component ◽  
Doubly Excited ◽  
State 1

Ab initio configuration interaction (CI) studies were performed on low-lying linear and nonlinear states of methinophosphide (HCP), using large basis sets with polarization and s, p Rydberg functions, and extensive multireference CI wave functions. Potential curves for linear states of HCP as functions of RCP and RCH and for nonlinear states as functions of αHCP were obtained, from which spectroscopic constants Te, Re, and ωe were evaluated. For the X1Σ+ ground state, the energy of dissociation into H + CP and the dipole moment were also calculated. The assignment of states based on the observed spectrum had to be revised in several instances. The ã state remained 13Σ+ (or 13A′), but the [Formula: see text] state became 13A″, the [Formula: see text] state, 13Δ, the à and [Formula: see text] states remained 11A″ and 21A′, respectively, [Formula: see text] was not seen as a seperate state, and [Formula: see text] became 13Σ−. In the energy range from 0 to 8 eV, 22 linear and 11 nonlinear stable states were found. Nonlinear states were stabilized for excitations from π(9a′, 2a″) into the in-plane component of π*, 10a′. Several doubly excited states of the type π2 → π*2 were bound, lying at relatively small excitation energies.

scholarly journals Chemically Accurate Excitation Energies With Small Basis Sets

2019 ◽  
Author(s):  
Emmanuel Giner ◽  
Anthony Scemama ◽  
Julien Toulouse ◽  
Pierre-Francois Loos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Density Functional ◽  
Chem Phys ◽  
Basis Set ◽  
Basis Sets ◽  
Excitation Energies ◽  
Functional Correction ◽  
The One ◽  
Range Density

<p>By combining extrapolated selected configuration interaction (sCI) energies obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) algorithm with the recently proposed short-range density-functional correction for basis-set incompleteness [Giner et al., J. Chem. Phys. 2018, 149, 194301], we show that one can get chemically accurate vertical and adiabatic excitation energies with, typically, augmented double-ζ basis sets. We illustrate the present approach on various types of excited states (valence, Rydberg, and double excitations) in several small organic molecules (methylene, water, ammonia, carbon dimer and ethylene). The present study clearly evidences that special care has to be taken with very diffuse excited states where the present correction does not catch the radial incompleteness of the one-electron basis set.</p>

scholarly journals Chemically Accurate Excitation Energies With Small Basis Sets

2019 ◽  
Author(s):  
Emmanuel Giner ◽  
Anthony Scemama ◽  
Julien Toulouse ◽  
Pierre-Francois Loos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Density Functional ◽  
Chem Phys ◽  
Basis Set ◽  
Basis Sets ◽  
Excitation Energies ◽  
Functional Correction ◽  
The One ◽  
Range Density

<p>By combining extrapolated selected configuration interaction (sCI) energies obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) algorithm with the recently proposed short-range density-functional correction for basis-set incompleteness [Giner et al., J. Chem. Phys. 2018, 149, 194301], we show that one can get chemically accurate vertical and adiabatic excitation energies with, typically, augmented double-ζ basis sets. We illustrate the present approach on various types of excited states (valence, Rydberg, and double excitations) in several small organic molecules (methylene, water, ammonia, carbon dimer and ethylene). The present study clearly evidences that special care has to be taken with very diffuse excited states where the present correction does not catch the radial incompleteness of the one-electron basis set.</p>

Modification of HAM/3 excitation energies for ΠΠ* transitions of linear molecules

1980 ◽  
Vol 58 (16) ◽  
pp. 1687-1690 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Excitation Energy ◽  
Explicit Expression ◽  
Excited States ◽  
Configuration Interaction ◽  
Excitation Energies ◽  
Carbon Suboxide ◽  
Numerical Examples ◽  
Energy Correction ◽  
Linear Molecules ◽  
Configuration Interaction Calculations

The excitation energies calculated by the HAM/3 procedure for ΠΠ* transitions in linear molecules can be internally inconsistent by as much as ± 0.6 eV. In the recent study by Åsbrink etal., the problem was avoided by adopting Recknagel's expressions and requiring the proper average ΠΠ* excitation energy. In this paper, we trace the small inconsistency back to its origin in HAM/3 theory and derive the analytical expression for the energy correction as well as Recknagel's formulas. Numerical examples studied include all seven linear molecules investigated by Åsbrink etal. The explicit expression for the correction enables us to perform meaningful configuration-interaction calculations on the excited states, as illustrated by the carbon suboxide molecule.

Excitation ofS1andS3Metastable Helium Atoms to Doubly Excited States

2009 ◽  
Vol 102 (15) ◽  
Author(s):  
M. Alagia ◽  
M. Coreno ◽  
H. Farrokhpour ◽  
P. Franceschi ◽  
A. Mihelič ◽  
...  
Keyword(s):  
Excited States ◽  
Helium Atoms ◽  
Doubly Excited States ◽  
Doubly Excited
Sign in / Sign up

Export Citation Format

Share Document