Clifford E. Dykstra
Phi Beta Kappa, 1974; University of California Regents
Fellow, 1975-1976; Alfred P. Sloan Research Fellow, 1979-1981; University of Illinois
School of Chemical Sciences Award for Excellence in Teaching, 1982,
1988; I.U.P.U.I. School of Science Research Award, 1996; Indiana University
Teaching Excellence Recognition Award, 1998; Editor, Journal of
Molecular Structure-Theochem, 1993-present; Glen Irwin Award, 2003.
Research
Our investigations involve the development of models,
theories, and computational methods for determining molecular structure,
energetics, properties, vibrational effects, and interactions. We
take full advantage of the latest computing capabilities when designing
new computational strategies, usually constructing uniform, extendable
procedures that have long-term utility.
Ab initio electronic structure theory is a conerstone of our efforts.
We have devised a number of state-of-the-art techniques for electron
correlation and for the direct evaluation of numerous molecular
propeties. Calculational studies using these methods provide highly
accurate bond lengths and bond angles, dipole and higher order electrical
moments, polarizabilities, hyperpolarizabilities, chemical shieldings,
and magnetic susceptibilities. The values obtained are used for
answering structural and energetic issues in an ever-widening range
of chemical problems.
A major area of study in recent years has been intermolecular interaction,
and our interests have focused on (i) studying small, weakly bound clusters
through ab initio (quantum mechanical) and model calculations, (ii) working
with several experimental groups to interpret special spectroscopic data for
complicated clusters, (iii) developing and applying ab initio methods for
molecular response properties needed for model potentials, (iv) carrying out
collaborative work on non-linear optical response in certain polymers, and
(v) investigating certain dynamical features of cluster behavior. An emerging,
connected interest is on a class of problems which have the potential for
impacting several technologies including hydrogen fuel storage, geological
and materials entrapment of carbon dioxide, and biomolecular modeling of
slippery energy landscapes. The focus with such applications is a fundamental
issue, the unique features of aggregating, quadrupolar molecules.
Quadrupolar molecules are those neutral molecules that have a zero permanent
dipole moment but a non-zero quadrupole moment (e.g., H2, N2, HCCH, ethane,
benzene, allene, and transoid-glyoxal). There are extended species with similar,
but local quadrupolar fields. For instance, polyynes, H(CC)nH, have interaction
sites that correspond to the influence of local –CC– quadrupoles. The orientational
and translational features of the interactions among quadrupolar species, such as
benzene, are simply not those of dipole-dipole interacting species. There are
special structural, energetic, and dynamical manifestations. For instance, in a
regular close-packing arrangement of hundreds of H2 molecules, each embedded
molecule has 12 nearest neighbors oriented in a way that corresponds to different,
favorable quadrupole-quadrupole interactions. The potential for rotating a single
molecule has a substantial barrier: The nearest neighbor interactions essentially
lock the orientation. Remarkably, the barrier goes almost to zero because the
nearest neighbor molecules can re-orient in a concerted manner.
There are interesting technological questions of packing of small assemblies of
quadrupolar species, e.g., hydrogen (related to storage of hydrogen as a fuel) and
carbon dioxide (for aggregation related to geological and materials entrapment),
and information on interactions is vital. Bigger molecules that may have a dipole
but also local quadrupolar sites, such as polystyrene, are also a target of our
interests. Our long-standing interest in the phenomena associated with weak,
non-covalent bonding of neutral molecules has brought us to realize that quadrupolar
molecules aggregate uniquely. They tend to have numerous binding sites (multiple
minima), surface flatness that allows for especially wide-amplitude vibrational
excursions, and often energetically-competitive packing arrangements.
Small
perturbations (fields, conformational changes, other nearby molecules, atoms, and
ions)
can have sharper effects than for clusters of dipolar molecules. Some
features may not yet have been
recognized, and clearly, the translation of molecular
properties into surface features and then into
dynamical effects remains an open
issue. It is likely to be an important issue for biomolecular and materials
simulations in the years ahead.
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Publications
M. Carmichael, K. Chenoweth, and C. E. Dykstra, J. Phys. Chem. A.
108, 3143-3152 (2004); Hydrogen Molecule Clusters.
C. E. Dykstra, J. Phys. Chem. A 197, 4196-4202 (2003); Significant
Low Order Effects in the Onset of Protonation and Related Interactions.
C. E. Dykstra, Adv. Chem. Phys. 126, 1-40 (2003); Intermolecular
Interaction: From Properties to Potentials and Back.
K. Chenoweth and C. E. Dykstra, J. Phys. Chem. A 106, 8117 (2002);
The Slippery Sliding Interaction of Acetylene with Polyynes.
E. Arunan, T. Emilsson, H. S. Gutowksy, G. T. Fraser, G. de Oliveira
and C. E. Dykstra, J. Chem. Phys. 117, 9766-9776 (2002); Rotational
Dynamics of the Weakly Bonded C6H6-H2S Dimer and Comparisons to
C6H6-H2O Dimer.
C. E. Dykstra and J. M. Lisy, J. Molec. Structure–Theochem 500,
375-390 (2000). Experimental and Theoretical Challenges in the Chemistry
of Noncovalent Intermolecular Interaction and Clustering.
T. Zhou and C. E. Dykstra, J. Phys. Chem. A 104, 2204-10 (2000).
Additivity and Transferability of Atomic Contributions to Molecular
Second Dipole Hyperpolarizabilities.
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