Calculation of exchange energies using algebraic perturbation theory

Calculation of Exchange Energies Using Algebraic Perturbation Theory

Calculation of Dissociation Energies Using Many - Body Perturbation Theory

A major task for theoretical chemists is the development of methods to predict energy differences with chemical accuracy. Most quantum chemists agree that accurate prediction of relative energies requires application of theories that include electron correlation effects, effects not treated in self-consistent-field (SCF) calculations [1-4]. Estimates of molecular correlation energy have been ob...

Excitation energies from density functional perturbation theory

We consider two perturbative schemes to calculate excitation energies, each employing the Kohn– Sham Hamiltonian as the unperturbed system. Using accurate exchange-correlation potentials generated from essentially exact densities and their exchange components determined by a recently proposed method, we evaluate energy differences between the ground state and excited states in first-order pertu...

Extending QCD perturbation theory to higher energies

On the basis of the results of a new renormalisation group improved small-x resummation scheme, we argue that the range of validity of perturbative calculations is considerably extended in rapidity with respect to leading log expectations. We thus provide predictions for the energy dependence of the gluon Green function in its perturbative domain and for the resummed splitting function. As in p...

Calculation of phononic and thermal properties of the CaB2 using the perturbation density functional theory (Research Article)

In this paper, the phononic structure and Enthalpy of CaB2 compound in simple hexagonal and orthorhombic phase have been investigated. The calculations were performed using the pseudo-potential method in the framework of the density functional theory and using the Quantum-Espresso code. Using the group theory and the characteristic table of the composition point group, the phonon modes were ide...