We perform first principles simulations for the structural, elastic and electronic properties of orthorhombic samarium orthoferrite $SmFeO_3$ within framework density functional theory. A number different functionals, such as local approximation, generalized gradient Hubbard interaction modified functional, Becke$-$Johnson approximation Heyd$-$Scuseria$-$Ernzerhof hybrid have been used to model...

Quantum cluster theories are a set of approaches for the theory of correlated and disordered lattice systems, which treat correlations within the cluster explicitly, and correlations at longer length scales either perturbatively or within a mean-field approximation. These methods become exact when the cluster size diverges, and most recover the corresponding (dynamical) mean-field approximation...

– We introduce an efficient method to solve the Bose-Hubbard model. The Schrödinger equation is solved by the successive construction of doorway states. The ground state wavefunction derived by this method contains all relevant many-body correlations introduced by the hamiltonian, but the dimensionality of the Hilbert space is greatly reduced. We apply the doorway method to obtain the chemical ...

Hirsch’s dynamic Hubbard model describes the effect of orbital expansion with occupancy by coupling the doublon operator to an auxiliary boson. We use the nonequilibrium dynamical mean field method to study the properties of doublon and hole carriers in this model in the strongly correlated regime. In particular, we discuss how photodoping leads to doublon and hole populations with different ef...

Energy spectra of fullerene C 50 and exohedral Cl 10 with the D 5h symmetry groups have been obtained within Hubbard model static fluctuation approximation. The energy states classified using methods group theory, allowed transitions in molecules determined. On basis spectrum is given an interpretation experimentally observed optical absorption bands molecule . Keywords: model, Green's function...

In this study, we examine the superconducting instability of a quasi-one-dimensional lattice in Hubbard model based on random-phase approximation (RPA) and fluctuation exchange (FLEX) approximation. We find that spin-singlet pair density wave (PDW-singlet) with center-of-mass momentum $2k_F$ can be stabilized when one-dimensionality becomes prominent toward perfect nesting Fermi surface. The ob...