3,833 research outputs found
Hybrid RHF/MP2 geometry optimizations with the Effective Fragment Molecular Orbital Method
The frozen domain effective fragment molecular orbital method is extended to
allow for the treatment of a single fragment at the MP2 level of theory. The
approach is applied to the conversion of chorismate to prephenate by chorismate
mutase, where the substrate is treated at the MP2 level of theory while the
rest of the system is treated at the RHF level. MP2 geometry optimization is
found to lower the barrier by up to 3.5 kcal/mol compared to RHF optimzations
and ONIOM energy refinement and leads to a smoother convergence with respect to
the basis set for the reaction profile. For double zeta basis sets the increase
in CPU time relative to RHF is roughly a factor of two.Comment: 11 pages, 3 figure
Hyperspherical Treatment of Strongly-Interacting Few-Fermion Systems in One Dimension
We examine a one-dimensional two-component fermionic system in a trap,
assuming that all particles have the same mass and interact through a strong
repulsive zero-range force. First we show how a simple system of three strongly
interacting particles in a harmonic trap can be treated using the
hyperspherical formalism. Next we discuss the behavior of the energy for the
N-body system.Comment: 5 pages. Original paper for EPJ ST in connection with the workshop
BEC2014 28-31 May 2014 in Levico Terme, Ital
Occurrence conditions for two-dimensional Borromean systems
We search for Borromean three-body systems of identical bosons in two
dimensional geometry, i.e. we search for bound three-boson system without bound
two-body subsystems. Unlike three spatial dimensions, in two-dimensional
geometry the two- and three-body thresholds often coincide ruling out Borromean
systems. We show that Borromean states can only appear for potentials with
substantial attractive and repulsive parts. Borromean states are most easily
found when a barrier is present outside an attractive pocket. Extensive
numerical search did not reveal Borromean states for potentials without an
outside barrier. We outline possible experimental setups to observe Borromean
systems in two spatial dimensions.Comment: 9 pages, 5 figures, published versio
Three-Body Halos in Two Dimensions
A method to study weakly bound three-body quantum systems in two dimensions
is formulated in coordinate space for short-range potentials. Occurrences of
spatially extended structures (halos) are investigated. Borromean systems are
shown to exist in two dimensions for a certain class of potentials. An
extensive numerical investigation shows that a weakly bound two-body state
gives rise to two weakly bound three-body states, a reminiscence of the Efimov
effect in three dimensions. The properties of these two states in the weak
binding limit turn out to be universal.
PACS number(s): 03.65.Ge, 21.45.+v, 31.15.Ja, 02.60NmComment: 9 pages, 2 postscript figures, LaTeX, epsf.st
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