zerothorder 
The zerothorder term gives the conventional shell model description.


The aim of this work is to present a perturbative expansion which differs from the usual expansions of quantum field theory in that it uses as zerothorder approximation a nonGaussian model.


The modified HamiltonJacobi equation for the deterministic component is then solved, and the resulting zerothorder trajectories are computed.


The zerothorder trajectories can hence be classified following this parameter, which indicates a transition between two different regimes for some value lying between 0 and 1.


In the classical case, the WKB approximation can only be applied when the thermodynamic potential has the LandauGinsberg form; the zerothorder approximation coincides with Kramer's approximation.


In the multiplescattering theory of Kdeuterium interactions, the firstorder correction to the zerothorder (asymptotic) value of the Kdeuterium elastic scattering amplitude is calculated, using Kohn's variational method for nuclear collisions.


Simplified procedures for generation of the selfconsistent charge densities and bond orders from their zerothorder counterparts in the PPP method are detailed.


The zerothorder results which show substantial electron shifts and features suggesting charge imbalance in the amine and alkylboron accompanying reaction are modified by a selfconsistent, linear αuponorbital charge adjustment method.


A simplified method of determining the molecular correlation energy by two separate calculations, one for the internal and one for the noninternal correlation energies, is extended to multiconfigurational zerothorder wavefunctions.


A simplified method of determining the molecular correlation energy by two separate calculations, one for the internal and one for the noninternal correlation energies, is extended to multiconfigurational zerothorder wavefunctions.


A proof is given that in a configuration interaction method the firstorder interaction space contains at most only twice as many spin functions as the zerothorder space.


The averaged coupledpair functional (ACPF) method gives consistently the best agreement with experiment, but can become intractable, as rather large zerothorder reference spaces can be required.


It can serve as a tool for analyzing the accuracy of approximate electron correlation methods and the validity of the HartreeFock wavefunction as the zerothorder approximation.


Different forms of the zerothorder Hamiltonian in secondorder perturbation theory with a complete active space selfconsistent


A new oneparticle zerothorder Hamiltonian is proposed for perturbation theory with a complete active space selfconsistent field (CASSCF) reference function.


The new zerothorder Hamiltonian has been tested on CH2, SiH2, NH2, CH3, N2, NO, and O2, for which full configuration interaction (FCI) results are available.


The zerothorder Hamiltonian H0 is the sum of effective monomer Fockians and the zerothorder wave functions are exact eigenfunctions of H0.


The zerothorder wave functions of the ground (X?1A1 or 1 1A1) and B?1A1 (or 2 1A1) excited states are appropriately described by the first and second eigenvectors of the TCSCF secular equations.


It gives a zerothorder description of the shortrange spin correlation while insuring a proper translational symmetry with an appropriate projection of the local spin function over the entire lattice.


The present derivation yields a family of twocomponent relativistic Hamiltonians which can be used as zerothorder approximation to the Dirac equation.

