scholarly journals Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

2018 ◽  
Author(s):  
Graham Fletcher ◽  
Colleen Bertoni ◽  
Murat Keçeli ◽  
Michael D'Mello
Keyword(s):  
Excited States ◽  
Software Package ◽  
Parallel Implementation ◽  
Valence Bond ◽  
Wave Functions ◽  
Massively Parallel ◽  
Hartree Fock ◽  
External Software ◽  
Single Configuration ◽  
Bond Method

This work describes the software package, Valence, for the calculation of molecular<br>energies using the variational subspace valence bond (VSVB) method. VSVB is a highly scalable ab initio electronic structure method based on non-orthogonal orbitals. Important features of practical value include: Valence bond wave functions of Hartree–Fock quality can be constructed with a single determinant; excited states can be modeled with a single configuration or determinant; wave functions can be constructed automatically by combining orbitals from previous calculations. The opensource software package includes tools to generate wave functions, a database of generic orbitals, example input files, and a library build intended for integration with other packages. We also describe the interface to an external software package, enabling the computation of optimized molecular geometries and vibrational frequencies.

scholarly journals Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

2018 ◽  
Author(s):  
Graham Fletcher ◽  
Colleen Bertoni ◽  
Murat Keçeli ◽  
Michael D'Mello
Keyword(s):  
Excited States ◽  
Software Package ◽  
Parallel Implementation ◽  
Valence Bond ◽  
Wave Functions ◽  
Massively Parallel ◽  
Hartree Fock ◽  
External Software ◽  
Single Configuration ◽  
Bond Method

This work describes the software package, Valence, for the calculation of molecular<br>energies using the variational subspace valence bond (VSVB) method. VSVB is a highly scalable ab initio electronic structure method based on non-orthogonal orbitals. Important features of practical value include: Valence bond wave functions of Hartree–Fock quality can be constructed with a single determinant; excited states can be modeled with a single configuration or determinant; wave functions can be constructed automatically by combining orbitals from previous calculations. The opensource software package includes tools to generate wave functions, a database of generic orbitals, example input files, and a library build intended for integration with other packages. We also describe the interface to an external software package, enabling the computation of optimized molecular geometries and vibrational frequencies.

scholarly journals Valence : A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

2019 ◽  
Vol 40 (17) ◽  
pp. 1664-1673
Author(s):  
Graham D. Fletcher ◽  
Colleen Bertoni ◽  
Murat Keçeli ◽  
Michael D'Mello
Keyword(s):  
Parallel Implementation ◽  
Valence Bond ◽  
Massively Parallel ◽  
Bond Method

HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: II. SIMPLIFICATION OF THE ORBITAL EQUATIONS

1966 ◽  
Vol 44 (12) ◽  
pp. 3227-3240 ◽  
Author(s):  
Maurice Cohen ◽  
Paul S. Kelly
Keyword(s):  
Total Energy ◽  
Excited States ◽  
Wave Functions ◽  
Lower State ◽  
Hartree Fock ◽  
Orthogonality Constraint ◽  
State Functions

Hartree–Fock wave functions have been calculated for a number of excited states of the helium sequence, the wave functions being constrained to be orthogonal to all lower state functions. The effect of choosing the inner 1s orbital so that the orthogonality constraint is satisfied automatically has been examined, and it is shown that such a choice has a very small effect on the total energy. An extension to heavier systems is proposed.

HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: III. DIPOLE TRANSITIONS IN THREE-ELECTRON SYSTEMS

1967 ◽  
Vol 45 (5) ◽  
pp. 1661-1673 ◽  
Author(s):  
Maurice Cohen ◽  
Paul S. Kelly
Keyword(s):  
Excited States ◽  
Wave Functions ◽  
Electron Systems ◽  
Matrix Elements ◽  
Isoelectronic Sequence ◽  
Hartree Fock ◽  
Transition Matrix Elements ◽  
Simplified Procedure ◽  
Good Agreement ◽  
Dipole Length

Hartree–Fock wave functions for a number of S, P, and D states of the lithium isoelectronic sequence have been calculated, using a simplified procedure described in an earlier paper. Transition matrix elements for all permitted dipole transitions between these states have been computed using both the dipole length and the dipole velocity formulations. The results are in good agreement with earlier calculations.

HARTREE–FOCK WAVE FUNCTIONS FOR EXCITED STATES: IV. OSCILLATOR STRENGTHS IN THE HELIUM ISOELECTRONIC SEQUENCE

1967 ◽  
Vol 45 (6) ◽  
pp. 2079-2090 ◽  
Author(s):  
Maurice Cohen ◽  
Paul S. Kelly
Keyword(s):  
Matrix Element ◽  
Excited States ◽  
Transition Matrix ◽  
Transition Matrix Element ◽  
Wave Functions ◽  
Oscillator Strengths ◽  
Isoelectronic Sequence ◽  
Hartree Fock ◽  
Good Agreement

Orbital wave functions for a number of singlet and triplet S, P, and D states of the helium sequence through C+4 have been calculated using an approximation described earlier. The wave functions have been employed to calculate the oscillator strengths for all allowed dipole transitions between these states, using both the length and velocity forms of the transition matrix element. Our results are in good agreement with the most accurate values available.

The molecular orbital theory of chemical valency XIII. Orbital wave functions for excited states of a homonuclear diatomic molecule

1953 ◽  
Vol 216 (1126) ◽  
pp. 424-433 ◽  
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Valence Bond ◽  
Present Theory ◽  
Wave Functions ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Bond Theory ◽  
Homonuclear Diatomic Molecules ◽  
Approximate Wave

The expansions for the exact wave functions for excited states of homonuclear diatomic molecules derived in part XII are used as the basis for discussing various approximate wave functions of the orbital type. The states considered in detail are the lowest states of symmetries 1 Σ u + , 3 Σ u + . The calculus of variations is used to determine the optimum forms for the component orbital functions. A transformation to equivalent orbitals is used to bring out the physical significance of the various wave functions, and to relate the present theory to earlier theories, in particular the molecular orbital theory, the valence-bond theory and their generalizations.

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