Computational Chemist:
Dr. Leonel Murga, Ph.
D. (Leo)
CBS 203, 626-6514
Profile:
I received my Ph. D. in Chemistry from Northeastern University in Boston, MA in 1999 working under the supervision of Dr. Mary Jo Ondrechen.
My
thesis work was divided mainly in two parts dealing with the unifying theme of
the effects of electric fields on molecular properties. The first part was
based on our research of the Stark Effect on Mixed-Valence systems. Stark
Effect Spectroscopy even though has been around for long time has traditionally
been an underutilized method; the decade of the nineties saw a renewal of
interest in the technique and we intended to understand the theoretical
foundations of its application to systems with mixed-valency. The second part
of my research work tried to understand the behavior of static hyperpolarizabilities
in oligomeric systems of alternating structure (A-B-A-B). Such alternating
systems are common in organic chemistry (e.g. polyacetelyne) but lately we have
seen very interesting organometallic oligomers (better described as
M-A-M-...) whose properties can be tuned by careful selection and modification
of the bridging ligands A.
During
my Ph. D. years at Northeastern, I also had the opportunity to work as a part
time intern in Moldyn, Inc. For those
of you familiar with the Molecular Mechanics programs Quanta and Discover,
Moldyn was the developer of a module able to perform molecular mechanics and
dynamics using a multi body approach. The methodology is applied better to
large systems (e.g. proteins) and in essence allows the user to divide the
system into smaller parts defined as bodies, which can be either rigid or
flexible. This aggregation process can greatly reduce computational cost thus
allowing for longer simulation times. The approach is actually an extension of
mechanics to the description of multi body systems that typically are found in,
for example, satellite and other aerospace crafts. This internship allowed
me to work in the areas of Molecular Mechanics and Dynamics using the CHARMM
package. I also explored the implementation of multiple time step integrators
that allow the separation of different motions according to their time scales;
this is important as it may drastically reduce computation times of dynamical
behavior by reducing the number of integration steps necessary in a simulation.
Currently
I spend my other half of the time working in the group of Dr. Jean-Luc Bredas
here at the University of Arizona. This has allowed me to learn and use methods
in the calculation of electronic properties mainly through the use of the
program Gaussian 98.
As
a part of my work during all these years, I have also developed numerical
methods and algorithms for the efficient solution of non-linear equations,
differential equations, matrix storage and multiplication in sparse systems,
eigenvalue and eigenvectors calculations and, procedures based on variations of
Lanczos and Cholesky algorithms.
Publications:
Murga, Leonel F.;
Ondrechen, Mary Jo; Numerical Aspects of the Calculations of Second
Hyperpolarizabilities Using the Finite Field Method and a Simple Lanczos
Algorithm. Accepted for publication in Journal of Computational Chemistry.
Murga, Leonel F.;
Shehadi, Ihsan; Ondrechen, Mary Jo; Models for Chemical Control of Third
Order Hyperpolarizabilities in Finite Polymers. Accepted for publication in
Trends in Chemical Physics.
Murga, Leonel F. Theory
of the Effects of Electric Fields on Molecular Properties. Ph. D.
Dissertation. 1999, Northeastern University, Boston.
Ferretti, Alessandro; Lami, Alessandro; Murga, Leonel F.; Shehadi,
Ihsan; Ondrechen, Mary Jo; Villani, Giovanni; Theory of Electroabsorption Spectroscopy in Pyrazine Bridged Ru Dimers. Journal of the American Chemical Society, 121,
2594-2596, 1999.
Murga, Leonel F.;
Ondrechen, Mary Jo; Theory of the Stark Effect in Protein Systems Containing
an Electron Donor-Acceptor Couple. Journal of Inorganic Biochemistry, 70,
245-252, 1998.
Murga, Leonel F.;
Ferretti, Alessandro; Lami, Alessandro; Ondrechen, Mary Jo. Theory of the
Stark Effect Spectral Lineshape for a Delocalized Mixed-Valence Complex. Inorganic
Chemistry Communications, 1, 137-140, 1998.
Shehadi, Ihsan;
Murga, Leonel F.; Ondrechen, Mary Jo; A Hubbard Model for the Second
Hyperpolarizability in Alternating Polymers. Chemical Physics Letters, 291,
325-332, 1998.
Murga, Leonel F.;
Ondrechen, Mary Jo; Potential Energy Surfaces for a Mixed-Valence Dimer in
an Applied Electric Field; Theoretica Chimica Acta, 90,
331,1995