Study of excited states of polyethylene in the Hartree–Fock, Tamm–Dancoff, and random‐phase approximations

1995 ◽  
Vol 102 (17) ◽  
pp. 6831-6836 ◽  
Author(s):  
Marjan Vrac̆ko ◽  
Benoît Champagne ◽  
David H. Mosley ◽  
Jean‐Marie André
Keyword(s):  
Excited States ◽  
Random Phase ◽  
Hartree Fock

β-DECAY HALF-LIVES AROUND 78Ni AND 132Sn IN A SELF-CONSISTENT APPROACH

2010 ◽  
Vol 25 (21n23) ◽  
pp. 2012-2013
Author(s):  
FUTOSHI MINATO ◽  
CHUNLIN BAI
Keyword(s):  
Excited States ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Particle Interaction ◽  
Tensor Force ◽  
Q Value ◽  
Β Decay ◽  
Quasiparticle Random Phase Approximation ◽  
Hartree Fock ◽  
Self Consistent

β-decay half-lives around 78 Ni and 132 Sn are studied with proton-neutron Quasiparticle Random Phase Approximation on the basis of Skyrme-Hartree-Fock (SHF) method. We take into account tensor force correlation in calculating the ground and excited states and find it improves the half-life of 132 Sn . However, the Q value is still underestimated. We also discuss that half-lives do not strongly depend on type of particle-particle interaction in isospin T = 0 channel.

Potential barrier effect and discrete structure o between 40 and 120 Å in the Rb I absorption spectrum

1975 ◽  
Vol 344 (1637) ◽  
pp. 303-309 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Absorption Maximum ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Particle Model ◽  
Discrete Structure ◽  
Model Calculations ◽  
Hartree Fock ◽  
Independent Particle ◽  
Independent Particle Model

Investigation of the Rb I absorption spectrum between 40 and 120 Å has revealed a broad absorption maximum in the 3d photoionization continuum, as well as discrete features associated with the excitation of a 3d-subshell electron. The discrete structure is identified, Hartree-Fock calculations of the transition energies are given and the absorption maximum is discussed in relation to similar spectra and to recent random phase approximation with exchange (r.p.a.e.) and independent particle model calculations.

scholarly journals Low-Cost Molecular Excited States from a State-Averaged Resonating Hartree-Fock Approach

2019 ◽  
Author(s):  
Jacob Nite ◽  
Carlos A. Jimenez-Hoyos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Low Cost ◽  
Computational Cost ◽  
Mean Field ◽  
Chem Phys ◽  
Spin Projection ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Orbital Relaxation

Quantum chemistry methods that describe excited states on the same footing as the ground state are generally scarce. In previous work, Gill et al. (J. Phys. Chem. A 112, 13164 (2008)) and later Sundstrom and Head-Gordon (J. Chem. Phys. 140, 114103 (2014)) considered excited states resulting from a non-orthogonal configuration interaction (NOCI) on stationary solutions of the Hartree–Fock equations. We build upon those contributions and present the state-averaged resonating Hartree–Fock (sa-ResHF) method, which differs from NOCI in that spin-projection and orbital relaxation effects are incorporated from the onset. Our results in a set of small molecules (alanine, formaldehyde, acetaldehyde, acetone, formamide, and ethylene) suggest that sa-ResHF excitation energies are a notable improvement over configuration interaction singles (CIS), at a mean-field computational cost. The orbital relaxation in sa-ResHF, in the presence of a spin-projection operator, generally results in excitation energies that are closer to the experimental values than the corresponding NOCI ones.

scholarly journals Low-Cost Molecular Excited States from a State-Averaged Resonating Hartree-Fock Approach

2019 ◽  
Author(s):  
Jacob Nite ◽  
Carlos A. Jimenez-Hoyos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Low Cost ◽  
Computational Cost ◽  
Mean Field ◽  
Chem Phys ◽  
Spin Projection ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Orbital Relaxation

Quantum chemistry methods that describe excited states on the same footing as the ground state are generally scarce. In previous work, Gill et al. (J. Phys. Chem. A 112, 13164 (2008)) and later Sundstrom and Head-Gordon (J. Chem. Phys. 140, 114103 (2014)) considered excited states resulting from a non-orthogonal configuration interaction (NOCI) on stationary solutions of the Hartree–Fock equations. We build upon those contributions and present the state-averaged resonating Hartree–Fock (sa-ResHF) method, which differs from NOCI in that spin-projection and orbital relaxation effects are incorporated from the onset. Our results in a set of small molecules (alanine, formaldehyde, acetaldehyde, acetone, formamide, and ethylene) suggest that sa-ResHF excitation energies are a notable improvement over configuration interaction singles (CIS), at a mean-field computational cost. The orbital relaxation in sa-ResHF, in the presence of a spin-projection operator, generally results in excitation energies that are closer to the experimental values than the corresponding NOCI ones.

Ab initio predictions of the zero field splittings and the singlet–triplet transition strengths for the n → π* transition of selenoformaldehyde

1993 ◽  
Vol 71 (10) ◽  
pp. 1706-1712 ◽  
Author(s):  
D.C. Moule ◽  
L. Chantranupong ◽  
R.H. Judge ◽  
D.J. Clouthier
Keyword(s):  
Energy Levels ◽  
Random Phase ◽  
Open Shell ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Hartree Fock ◽  
Lower Valence ◽  
Polarization Functions

The energy levels of the lower valence and Rydberg states of selenoformaldehyde, CH2Se, have been calculated by the SCF/CI method. Wavefunctions for the ROHF (restricted open shell Hartree–Fock) states were obtained with the Binnings–Curtis double-ζ basis set, augmented with Rydberg and polarization functions. Configuration interaction was applied to the parent configurations, PCMO (parent configuration molecular orbital). Oscillator strengths were evaluated for the allowed electric dipole transitions by the RPA (random phase approximation), and SOPPA (second-order polarization propagator approximation) methods. The spin-orbit contribution to the zero field splitting of the first triplet state, 3A2(n,π*) as well as the oscillator strengths to the three spin components were calculated by perturbation theory. These calculations predict that the Sx, Sy, and Sz components are shifted by −96.091,−96.707, and + 29.167 cm−1, respectively, from their unperturbed position. The oscillator strengths for the three components fx, fy, and fz of the 3A2(n,π*) ← 1A1(g.s.) transition were calculated to be 3.45 × 10−7, 1.15 × 10−7, and 173.0 × 10−7.

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