Published in Interface. Vol. 2, No. 2, May 1994

Auburn University

by James Newhouse

Theory calculations in Chemistry and Physics, finite element analysis in Mechanical and Civil Engineering, and process simulation in Chemical Engineering are just some of the fields in which supercomputing on the ASN plays a significant role at Auburn University.

Prof. M. Squillacote in Chemistry has been interested in the entropic contribution to the energy difference of axial and equatorial methylcyclohexane and has calculated the vibrational frequencies and vibrational entropies for these two molecules. Theory calculations using Gaussian 92 combined with experimental work have shown the energy difference between these two seminal conformers to be entropically derived. He has also investigated, through calculations, the loss of molecular nitrogen from a series of 3,4-unsaturated azo compounds, and the stereospecificity and regiospecificity in the ENE reaction of alkenes and singlet oxygen for which perepoxides are the intermediates.

Prof. M. S. Pindzola in Physics is bringing calculations involving time-dependent Schrodinger and Dirac equations to both the C90 and the nCUBE. He is also bringing R-matrix calculations for electron-atom scattering to both machines. These codes, once tested on the ASA machines, will be used in production on a 16-processor C90 at Lawrence Livermore and a 500-processor Intel Paragon at Oak Ridge National Laboratory.

Prof. An Ban Chen's research focuses on the calculation of the electronic structure of semiconductors and alloys and the application of electronic structures to various materials properties. Recently, he has made systematic calculations of the variation of band gap as a function of alloy concentration for a large number of III-V and II-VI semiconductor alloys. These results will be compiled into a chapter of a book that he is writing, and they are useful to semiconductor physicists and to engineers working on micro-electronics and opto-electronic devices.

Prof. Timothy Placek in Chemical Engineering runs chemical process simulations similar to those done using the code Aspen, but with his own codes, written specifically for the paper pulp industry.

Prof. Joseph Tedesco and his graduate students have used the ASN to conduct finite element analyses of various types of engineering structures. Currently, he is involved in analyzing the dynamic response of concrete structures under high-strain-rate or impulse-loading and analyzing highway bridge structures in Alabama to determine vehicle load distribution.

Prof. Mike McKee's research involves the application of supercomputers to solving problems in inorganic chemistry. He calculates the total energies of molecules from first principles, i.e., ab initio. Geometries are computed by minimizing the energy with respect to motion of the atoms within the molecule and reaction paths are constructed by "leading" the molecule over the highest point on the "potential energy surface" to products. These studies shed light on the kinetics of reactions, which is of interest in a number of diverse fields including biology, chemical engineering, and chemical syntheses.

Prof. Charles Neely and his colleague Irene Newhouse are using semi-empirical molecular-orbital-theory codes on the Cray to understand the oxidation reactions of toxic pollutants in a silent discharge plasma. The experimental side of this work is done in collaboration with Prof. Eugene Clothiaux of the Physics Dept.; they hope to be able to scale this method up to a practical process. They are also using the molecular dynamics code Amber to model dipalmitoylphosphatidylcholine Langmuir-Blodgett films in order to understand their differing interactions with the odorants R-carvone and S-carvone. The two compounds, mirror images, smell different; up to now, it has been felt that proteins are necessary for such chiral recognition.

Figure 2 is an image from the graphic-user-interface program Spartan and depicts a substituted carborane (with an unusual carbene functional group), subject of calculations by Professor Mike McKee. Shown is the highest occupied molecular orbital (rounded solid shapes) and the total electron density (mesh).