Julio Facelli
Project Title:
Modeling 13-C and 15-N Chemical Shifts in Crystalline systems.
Contact Person(s) (Individual, Institution, city, country, email) :
Dr Julio C. Facelli
Director
UNIVERSITY OF UTAH
CTR FOR HIGH PERFORM COMPUTING
155 SOUTH 1452 EAST RM 405
SALT LAKE CITY UT 84112-0190
Phone (801)-581-7529
Fax (801)-585-5366
e-mail facelli@chpc.utah.edu
Potential Collaborators (including contact
people) (Individual, Institution, city, country, email) :
Dr. Marta Ferraro
Departamento de Fisica
Universidad de Buenos Aires
1428 Buenos Aires Argentina
marta@dfuba.df.uba.ar
Project URL (if one exists) :
n/a
Application Description (1-2 paragraphs):
Nuclear Magnetic Resonance (NMR) spectroscopy is one of the most important tools
for characterizing the structure of organic, biological macromolecules and
inorganic materials. Increasingly, researchers use solid state NMR to
characterize great variety microscopic structures. A common complication of NMR
spectra in solid state is the duplication of lines corresponding to formally
magnetically equivalent nuclei due to intermolecular or crystalline effects.
Conversely, if properly modeled, these minor deviations from the corresponding
liquid spectrum may be used to investigate details in the crystalline structure
and to remove ambiguities in the assignment of lines in the NMR solid state
spectra. Computer hardware and software have reached the point that modeling
these effects may be an achievable goal. Existing quantum mechanical methods in
use to predict NMR nuclear shielding do not use crystalline wave functions to
evaluate the shift tensor components; consequently, the theoretical results do
not include any intermolecular contributions to the shielding.
This proposal request supplemental funding to accelerate the collaboration
between the NMR research groups at the University of Utah and Universidad de
Buenos Aires (Argentina). These groups are developing computational tools to
model the intermolecular effects observed on the NMR chemical shieldings
measured in the solid state. The combined expertise and resources of these two
groups have the potential to make significant faster progress in this field.
The calculation of chemical shielding in
systems of real interest with periodic boundary conditions, will require
calculations in crystals with more than 30-40 atoms in the unit cell. We
anticipate needing a great deal of computer power. All the code develop will
use, as much as possible, parallel computer techniques. We will use the MPI
standard to make the code highly portable to different parallel architectures
available at the Center for High Performance Computing. Several of the molecules
that have been studied by the Utah group in detail (naphthalene, benzamide,
pyrene, imidazole, etc.) will be used to test the accuracy of the methods
develop here. The PIs are familiar with the NMR as well as the high quality
diffraction data existing for these molecules.
Finally, we will try to use the new software developed under this program to
further explore the use of NMR as a tool for quantitative structural elucidation
when diffraction data may not be available. To this end this program could be
used as intermediate to correlate crystal geometry and chemical shifts. When
this feature is added to a crystal modeling program, it will be possible to use
the experimental NMR chemical shifts as additional constrains to the
optimization of the crystal structure. These techniques have been used
extensively with NOEs and J couplings (Karplus type of equations) to solve
molecular structures in liquids. The missing link to use the same approach in
solids using the NMR chemical shifts is a robust method to calculate the nuclear
shielding in crystalline systems.
Application Type (select one):
___ Biology
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