Recent advances in explicitly-correlated electronic structure methods4/22/09 4:00pmMIT Building 24, Room 121Edward Valeev
Virginia Tech
Many problems in molecular sciences (bond energetics, spectroscopy, weak interactions, etc.)
require highly-accurate and systematically-improvable
description of electronic structure. The traditional many-body methods, such as the celebrated
coupled-cluster (CC) method, can be used to approach the exact solution, but are severely
limited by the slow convergence of the error with respect to the size of the basis set.
This so-called basis set problem of the many-body methods is rooted in the
inappropriate form of the many-electron expansions used in the traditional methods.
Here I will briefly review the history of explicitly-correlated many-body methods, which
can be considered the first-principles solution to the basis set problem,
and discuss the recent development of practical R12 methods pursued in several
groups around the world. In particular, I will highlight our group's work in the area
of perturbative R12 methods, which are especially simple without any loss of robustness.
We typically observe that an R12 method need only a modest triple-zeta basis set to match
the precision of its more expensive quintuple-zeta standard counterpart.
In closing I will discuss a universal R12 approach that can be used to improve
any traditional and non-traditional many-body methods.