Abstract

The objective of this thesis is to compare the upper bound of the ground state energy of doubly ionized carbon (C⁺⁺) to the lower bound obtained by reduced density matrices.

To make a fair comparison, the number of orbitals used in both is the same, namely ten. The upper bound is obtained by use of the standard Rayleigh-Ritz Variational Principle which states ⟨Ψ|H|Ψ⟩ ≥ Eo(H) were Eo(H) is the exact ground state energy, H is the Hamiltonian, and Ψ is the trial wave function.

Abstract An improved ground state wavefunction for Helium for use in density matrix calculations has been obtained. This improvement was achieved by the introduction into the expansion for the singlet S-state wavefunction for Helium, of a term containing explicit angular dependence. This angular term was constructed so as to preserve angular momentum symmetry by being an eigenfunction of the two-particle, angular momentum operator with eigenvalue zero, as is required for S-states. The results give...

Abstract The intention of this paper is to determine some of the properties of the screened coulomb [sic] potential, and look into its validity as a model for observed emission spectra of hydrogen plasmas. Some variational methods will be examined and the problem of finding upper bounds to the excited states of atoms will also be investigated. The variational method is then applied to the anomoly [sic] of the...

Abstract The solution to the problem of a one-electron ion under the influence of various generalized central-field potentials is considered. Solutions are obtained using a finite expansion of the perturbation wave functions in terms of associated Laguerre polynomials. Higher orders of perturbation theory are obtained without having to perform integrations over the continuum states, and the solution can be written explicitly to any order. This perturbation procedure is applied to the three...

Abstract

A recently developed theory enabling the construction of density matrices which are expressible in terms of a given spin geminal set and which are a nearly N-representable as possible is discussed.

Calculation of lower bounds to the ground state energy of the C⁺⁺ ion is performed utilizing reduced density matrices subject to the continuously variable N-representability constraint determined by the above mentioned theory.

Abstract The objective of this paper is to demonstrate the usefulness of density matrix techniques in the determination of the ground state energy of certain atomic systems. Use of the method, currently under development, results in a lower energy bound in contrast with the Rayleigh-Ritz method which yields an upper bound. The former technique is illustrated for the C⁺⁺ atomic system. It was found that the Pauli Principle was being violated even when the 2-particle density matrix is expanded in...

Abstract In Part I, a large parameter asymptotic expansion of a perturbed simple harmonic oscillator is presented. Perturbations of the form λx∝ are studied were λ is the coupling constant. The method is demonstrated by a general derviation of the wavefunctions to third order for any ∝ and quantum number n. Additonal expressions are presented for the ground states to tenth order in the energy. It is also shown that the "matching condition" for the basic and...

Introduction Section II of this thesis considers the problem of an electron which is both bound in an attractive screened Coulomb potential and under the simultaneous influence of an external electric field. The total energy Hamiltonian, for the case of one electron immersed in a plasma, is derived. A suitable ground state wavefunction is chosen which incorporates the approximate induced dipole character of the charge configuration when subjected to the plasma's free particle uniform electric field....

Abstract The non-relativistic energies have been determined for the singlet and triple S states (1¹S, 2¹S and 2³S) of the helium like two electron system. Calculations were based on a finite set of orbitals of the order 7. The set, which includes Laguerre polynomials, is expressed as a superposition of configurations built up from one-electron wave functions or orbitals and approximates the exact wave function. Application of the variational principle leads to a system of linear equations....