4,134 research outputs found
The Effective Fragment Molecular Orbital Method for Fragments Connected by Covalent Bonds
We extend the effective fragment molecular orbital method (EFMO) into
treating fragments connected by covalent bonds. The accuracy of EFMO is
compared to FMO and conventional ab initio electronic structure methods for
polypeptides including proteins. Errors in energy for RHF and MP2 are within 2
kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides
similar to FMO but obtained two to five times faster. For proteins, the errors
are also within a few kcal/mol of the FMO results. We developed both the RHF
and MP2 gradient for EFMO. Compared to ab initio, the EFMO optimized structures
had an RMSD of 0.40 and 0.44 {\AA} for RHF and MP2, respectively.Comment: Revised manuscrip
Measurement of the neutron electric dipole moment by crystal diffraction
An experiment using a prototype setup to search for the neutron electric
dipole moment by measuring spin-rotation in a non-centrosymmetric crystal
(quartz) was carried out to investigate statistical sensitivity and systematic
effects of the method. It has been demonstrated that the concept of the method
works. The preliminary result of the experiment is ecm. The experiment showed that an accuracy of ecm can be obtained in 100 days data taking, using available
quartz crystals and neutron beams.Comment: 13 pages, 4 figure
Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions
Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated consistently, and applied to Li. The same two-body
interactions between the three particles are used to calculate the ground state
structure and the final state of the reaction processes. We reproduce the
available momentum distributions from Li fragmentation, together with
the size and energy of Li, with a neutron-core relative state containing
a -state admixture of 20\%-30\%. The available fragmentation data strongly
suggest an -state in Li at about 50 keV, and indicate a -state
around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file
attached at the end of the LaTeX file). To be published in Phys. Rev.
Measurement of the neutron electric dipole moment via spin rotation in a non-centrosymmetric crystal
We have measured the neutron electric dipole moment using spin rotation in a
non-centrosymmetric crystal. Our result is d_n = (2.5 +- 6.5(stat) +-
5.5(syst)) 10^{-24} e cm. The dominating contribution to the systematic
uncertainty is statistical in nature and will reduce with improved statistics.
The statistical sensitivity can be increased to 2 10^{-26} e cm in 100 days
data taking with an improved setup. We state technical requirements for a
systematic uncertainty at the same level.Comment: submitted to Phys. Lett.
Universality of three-body systems in 2D: parametrization of the bound states energies
Universal properties of mass-imbalanced three-body systems in 2D are studied
using zero-range interactions in momentum space. The dependence of the
three-particle binding energy on the parameters (masses and two-body energies)
is highly non-trivial even in the simplest case of two identical particles and
a distinct one. This dependence is parametrized for ground and excited states
in terms of {\itshape supercircles} functions in the most general case of three
distinguishable particles.Comment: 3 pages, 1 figure, published versio
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