Model Hamiltonians for strongly correlated
systems from Quantum Chemistry
Prof. F. Illas, Universitat de Barcelona, Espagne
e-mail:f.illas@qf.ub.es
Mercredi 14 février 2007, 10h15
Model Hamiltonians are simplifications of the exact Hamiltonian but which
are though to be able to describe the physics of a given system or family
of systems. The Heisenberg and the t-J model Hamiltonians are well-known
examples broadly used in solid state physics to describe strongly
correlated systems such as the high critical temperature superconducting
cuprates. However, a weak point of this approach lies in the fact that
model Hamiltonians are defined through parameters which are usually fitted
to reproduce experimental data. In this talk I will present a bottom-up
approach which permits to define well defined model Hamiltonians from
accurate quantum chemical calculations based either on explicitly
correlated wave functions or on density functional theory. For the latter,
new methodological aspects will be presented which show the weak point of
this approach.