Constrained variation method for excited‐state energies of atoms and molecules

1973 ◽  
Vol 59 (4) ◽  
pp. 1721-1725 ◽  
Author(s):  
P. S. C. Wang ◽  
Margaret Lowe Benston ◽  
D. P. Chong
Keyword(s):  
Excited State ◽  
Variation Method ◽  
Atoms And Molecules ◽  
Constrained Variation

Spin-polarized hydrogen, deuterium, and tritium: I. Ground-state energy calculated by a lowest order constrained-variation method

1989 ◽  
Vol 67 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Magne Haugen ◽  
Erlend Østgaard
Keyword(s):  
Binding Energy ◽  
Molar Volume ◽  
Ground State ◽  
Particle Density ◽  
Variation Method ◽  
Ground State Binding Energy ◽  
Spin Polarized ◽  
Hydrogen Deuterium ◽  
Constrained Variation ◽  
Theoretical Results

The ground-state energy of spin-polarized hydrogen, deuterium, and tritium is calculated by means of a modified variational lowest order constrained-variation method, and the calculations are done for five different two-body potentials. Spin-polarized H↓ is not self-bound according to our theoretical results for the ground-state binding energy. For spin-polarized D↓, however, we obtain theoretical results for the ground-state binding energy per particle from −0.42 K at an equilibrium particle density of 0.25 σ−3 or a molar volume of 121 cm3/mol to + 0.32 K at an equilibrium particle density of 0.21 σ−3 or a molar volume of 142 cm3/mol, where σ = 3.69 Å (1 Å = 10−10 m). It is, therefore, not clear whether spin-polarized deuterium should be self-bound or not. For spin-polarized T↓, we obtain theoretical results for the ground-state binding energy per particle from −4.73 K at an equilibrium particle density of 0.41 σ−3 or a molar volume of 74 cm3/mol to −1.21 K at an equilibrium particle density of 0.28 σ−3 or a molar volume of 109 cm3/mol.

Pseudopotential Theory for Atoms and Molecules

1977 ◽  
Vol 32 (8) ◽  
pp. 829-839 ◽  
Author(s):  
Levente Szasz
Keyword(s):  
Wave Function ◽  
Arbitrary Number ◽  
Valence Electron ◽  
Variation Method ◽  
Exact Equation ◽  
Pseudopotential Theory ◽  
Atoms And Molecules ◽  
Orthogonality Conditions ◽  
Valence Electrons ◽  
The Many

Abstract An exact pseudopotential theory is presented for atoms and molecules with arbitrary number of valence and core electrons and arbitrary number of nuclei. Using the variation method an equation is derived for the best many-valence-electron wave function which is orthogonalized to the core orbitals. Using this equation the exact equation is derived for the many-valence-electron pseudo-wavefunction which does not have to satisfy any orthogonality conditions. The Hamiltonian of the pseudopotential equation is of surprisingly simple structure and does not depend on the energy and/or on the wave function of the valence electrons. It is shown that the simple model Hamiltonian which is used in many pseudopotential calculations can be derived from the exact equation by two plausible approximations. The theory is elucidated on the example of atoms with two valence electrons.

Spin-polarized hydrogen, deuterium, and tritium: II. Pressure and compressibility calculated by a lowest order constrained-variation method

1989 ◽  
Vol 67 (7) ◽  
pp. 649-656 ◽  
Author(s):  
Magne Haugen ◽  
Erlend Østgaard
Keyword(s):  
Molar Volume ◽  
Ground State ◽  
Particle Density ◽  
Variation Method ◽  
Density Region ◽  
Spin Polarized ◽  
Hydrogen Deuterium ◽  
Constrained Variation ◽  
Ground State Energies ◽  
Theoretical Results

The pressure and the compressibility of spin-polarized H↓, D↓, and T↓ are obtained from ground-state energies calculated by means of a modified variational lowest order constrained-variation method. The pressure and the compressibility are calculated or estimated from the dependence of the ground-state energy on density or molar volume, generally in a density region from 0 to 1.5σ−3 corresponding to a molar volume of more than 20 cm3/mol, where σ = 3.69 Å (1Å = 10−10 m); the calculations are done for five different two-body potentials. Theoretical results for the pressure are 54.1–57.9 atm for spin-polarized H↓ 18.4–23.4 atm for spin-plolarized D↓, and 5.6–12.9 atm for spin-polarized T↓ at a particle density of 0.50σ−3 or a molar volume of 60 cm3/mol (1 atm = 101 kPa). Theoretical results for the compressibility are 51 × 10−4 −54 × 10−4 atm−1 for spin-polarized H↓, 108 × 10−4 −120 × 10−4 atm−1 for spin-polarized D↓, and 162 × 10−4 −224 × 10−4 atm−1 for spin-polarized T↓ at a particle density of 0.50σ−3 for a molar volume of 60 cm3/mol. The relative agreement between results for different potentials is somewhat better for higher densities.

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