THEORETICAL CHEMISTRY NEWS

Bulletin of the

Subdivision of Theoretical Chemistry of the

American Chemical Society

 

Vol. 21, No. 1 Summer 2000

News from the Theoretical Chemistry Subdivision

-- Reported by Ken Jordan, Subdivision Chair

The Executive Committee of the Theory Subdivision, which consists of current and past officers, met Sunday, March 26, at the San Francisco ACS meeting. Present were Mark Gordon, Ken Jordan, Michael Page, Richard Stratt, Fritz Schaefer, and Suzi Tucker. Topics discussed at the meeting included the IBM graduate student computational chemistry awards, ideas for future symposia, and suggestions for the appointment of the nominating committee to choose the next Vice Chair of the Subdivision.

Following the advice of the Executive Committee, Anne Chaka of Lubrizol and Marshall Newton of BNL were selected to join me in the capacity of a nominating committee to select the next Vice Chair. The nominating committee proposed Martin Head-Gordon for the position, and I am pleased to report that he has agreed to serve. Martin will begin his term as Vice Chair at the conclusion of the Fall ACS meeting, and will succeed to Chair Elect in 2002 and to the Chair of the Division in 2003.

This year's competition for the IBM graduate Fellowships had twenty high quality applications. The selection committee of Suzi Tucker, Jamie Coffin (of IBM), and myself had a hard time choosing the two recipients from this excellent pool. The two recipents are Graemme Henkelman and Holly Randa. Graemme is a graduate student at the University of Washington working with Prof. Hannes Jonsson. His proposal was entitled "Chemical Reactions on Semiconductor and and Metal Surfaces." Holly is a graduate student working with Greg Voth at the University of Utah. Her proposal was entitled "Ion Transport in Channels."

Congratulations to Graemme and Holly, and thanks to Jamie Coffin and IBM for their continued support of these awards and to Don Truhlar and the Minnesota Supercomputing Center for making available grants of CPU time for the awardees.

The computational Chemistry Awards will be given again this coming year. Professor Suzi Tucker, Chair-Elect of the Subdivision, will be in charge of the competition.

Several excellent suggestions for symposia topics were raised over our lunch meeting, and I passed these along in my report at the Physical Chemistry Division Executive Committee meeting on Sunday evening. As always, we welcome suggestions for symposia for the national meetings. Please send your suggestions along to Suzi Tucker, who will be rotating into the Chair position after the Fall meeting.

We would also like to remind faculty who are members of the Subdivision to encourage their students and postdoctoral fellows to join both the Theory Subdivision

And the Physical Chemistry Division.

Hope to see you all at the Fall meeting in DC.

-Ken

Please visit the subdivision web page at

http://quantum.chem.ndsu.nodak.edu/acs/

Theoretical Chemistry Postdoctoral Position Clearinghouse:

The Subdivision continues to run a clearinghouse for people looking to hire postdocs and people looking for postdoc positions. Currently there is a list of those looking for a position and one for those looking to hire, both of which are available on the Subdivision Web page. If you wish to be on either list, please send Mike e-mail or drop him a line. The address to contact him is:

Prof. Michael Page

Dept. of Chemistry

North Dakota State University

Fargo, ND 58105, USA

TEL: (701) 231-8291

E-mail: mike_page@ndsu.nodak.edu

 

 

Membership

The subdivision now has about 800 members. To join:

If you are already a dues-paying member of the Division of Physical Chemistry ($7.00/year, $2.00 for students), just send a note to the secretary of the Subdivision (Michael Page, Department of Chemistry, North Dakota State University, Fargo, ND 58105,USA mike_page@ndsu.nodak.edu)

indicating your wish to join. Please state that you are already a member of the Division.

If you are not already a member of the Division of Physical Chemistry but you do belong to the ACS, join the Division by sending a note to Professor Mark Gordon, Ames Laboratory, Iowa State University, Ames, IA 50011, USA, enclosing a check for $7.00 ($2.00 for students) and stating your wish to join the Subdivision at the same time.

 

--Call for Applicants

(Note 10-20 deadline!)

IBM Graduate Student Awards in Computational Chemistry

Below is an announcement for two Awards in Computational Chemistry that are open to current graduate students. We are grateful to

IBM and the Minnesota Supercomputing Institute for their support of these awards.

Let me urge you to encourage your graduate students to apply. The competition is open to any graduate student (regardless of citizenship) who began graduate study after August 1, 1997 and who is an ACS member (or whose advisor is an ACS member). These awards are designed to encourage graduate work in computational chemistry, to recognize research accomplishments, and to stimulate interest in the Subdivision of Theoretical Chemistry and the Physical Chemistry Division of the ACS.

An Awards Committee will consider all the applicants. The awards applications should be sent to Professor Suzi Tucker at the University of California, Davis. Note that the deadline for applications October 20, 2000.

These two awards, supported by IBM,

will provide one-time cash stipends of $2500 and $1000 as supplements to normal

financial aid to doctoral candidates in the research-dissertation stage in the 2000-2001 academic year. The Minnesota Supercomputing Institute will provide each awardee up to 1000 node-hours on an IBM

SP2 cluster for the awardees to actually carry out a portion of the awarded research. The

awardees will have access to the consulting services of the Institute normally available to all users. Awardee selection will be made on a competitive basis. Applicants should be working on new and innovative computational chemistry methods or applications in theoretical chemistry.

Applicants should prepare a written description of a computational chemistry research project that requires high performance computing, with

an explanation of the scientific importance of the project. Proposals need to include an estimate of the computing resources required in SP2 cpu-hours. Applicants should explain how they plan to use the grant funds. Two letters of recommendation, including one from the student's advisor, along with a vita and transcript, are required. The proposal, including the vita, should not exceed five double-spaced pages. In addition, a faculty person (typically the applicant's research advisor) responsible for the applicant's use of the Minnesota Supercomputing Institute resources must be identified.

Forward applications by October 20, 2000 to

Professor Susan Tucker

Department of Chemistry

University of California, Davis

Davis, CA 95616

tucker@chem.ucdavis.edu

The awardees will be announced in the Fall 2000 Subdivision newsletter.

Online Access: "Parallel Computing in Chemical Physics"

Elsevier Science Publishing is offering for a limited time free access to this special issue of Computer Physics Communications. The URL is

http://www.elsevier.nl/gej-ng/10/15/40/58/25/show/

NSF Rotator Positions

The National Science Foundation seeks scientists to serve in temporary (rotator) positions in Theoretical and Computational Chemistry. Interested individuals are encouraged to contact the Theoretical Chemistry Subdivision (Suzi Tucker, tucker@chem.ucdavis.edu, 530-752-2203)

Symposium Reports

The following are reports from the Spring 2000 national ACS meeting in San Francisco. We thank the symposium organizers for taking the time to put these wonderful reports together for us.

Awards Symposium : reported by Martin Head Gordon

ACS Award in Theoretical Chemistry (sponsored by IBM). Ernest Davidson's award lecture began with an overview of the status of quantum chemical models. Current methods are often advertised as being "black box" in nature, but this is not really true at present. He discussed two examples that illustrate this point, as well as being interesting chemistry. The first was the Cope rearrangement, where restricted models don't work, and unrestricted potential surfaces can exhibit unphysical bumps. The second example compared theory and experiment of orbital momentum profiles.

Peter Debye Award in Physical Chemistry (sponsored by Dupont). Peter Wolynes' Debye lecture had the central theme that new

concepts in physical chemistry must emerge at the mesoscopic level in order to capture the essential features of phenomena that involve

collective motions of very large numbers of atoms. This is distinct from the popular alternative of atomistic modeling, which may not be either insightful or even feasible for problems on this scale. Wolynes

focused particularly on the protein folding problem and factors that distinguish good folders from poor folders.

 

Patterning, Functionalization, and Reactivity of Complex Solid Surfaces:

Reported by Doug Doren

Aaron Golumbfskie described Kinetic Monte Carlo studies of disordered heteropolymer adsorption on patterned surfaces. He showed that special matching relations between the statistical features of the surface pattern and the heteropolymer can lead to selective adsorption of

polymers in regions of the surface where the pattern is suitably matched.

Robin Selinger described analytical stability analyses and mesoscale Monte Carlo simulations of the ordering in liquid crystals induced by patterns on an anisotropic substrate. She showed that the substrate can affect the liquid-crystal structure only locally, and not in the bulk, but that chirality of the molecules can affect the bulk structure and its response to electric fields.

David Sholl discussed atomistic models of the interactions between chiral molecules and vicinal metal surfaces that have inherent chirality. Monte Carlo simulations were used to study the spectrum of configurations and interactions that lead to differences in the interaction free energy of

stereoisomers. The theoretical results agree closely with recent experiments.

 

 

 

Physical chemistry of Chirality: Reported by Dave Beratan

Laurence Barron in his invited talk discussed new insights into solution structure and dynamics of proteins, nucleic acids, and viruses from Raman optical activity. Later in a contributed talk, he considered symmetry aspects of molecular chiralty

Jeff Cina described collaborative research with R. Harris on the theory of nonlinear spectroscopy using well defined phase relations between incident light pulses (4 pulse experiments). Potential applications in chirality relate to potential pump-dump methods that would drive stereoselective photo-racimization.

Josef Michl described molecular dynamics simulations of how a flow of noble gas atoms across an array of chiral "propellar" molecules might lead to their collective rotation with a particular handedness. Simulations are suggesting target synthetic structures for "molecular turbines".

AD Buckingham presented a summary of tensor theory of optical activity and sum frequency harmonic generation.

Bob Harris presented a correlation function theory of nonlinear optical response derived from chiral molecules in solution and signatures for chiral fluctuations of molecules.

Andy Albrecht described a three-state model for the first hyperpolarizability of chiral systems in isotropic solution.

David Beratan described the used of molecular fragmentation and optical rotation angle computation strategies for assigning the absolute stereochemistry of chiral natural products with multiple stereocenters. He discussed assignment of atomic and group contributions to optical rotation angles.

Jim Cheeseman discussed basis set dependence of optical rotation angles obtained from ab initio calculations.

 

 

 

 

 

POTENTIAL ENERGY SURFACES: FROM POLYATOMICS TO MACROMOLECULES Reported by Bill Hase and Liem Dang

George C. Schatz: Methods were described for representing multi-dimensional potential energy surfaces for molecular dynamics simulations. These methods include both global and local interpolation, and hybrid methods that treat subsets of the degrees of freedom differently. Specific methods described are the reducing kernel Hilbert space, Shepherd interpolation, and moving least squares.

Albert Wagner: A variational transition state theory (VTST) approach, which is an extension of phase space theory, was described for calculating bimolecular rate constants for barrierless association reactions. The long-range fragment-fragment Hamiltonian is used as in phase space theory, with the complete anisotropic intermolecular potential, however a variable reaction coordinate (VRC) as described by Stephen Klippentstein is used, instead of the center-of-mass reaction coordinate. Ab initio information may be used directly in the VTST calculation. A more general approach may involve the use of semiempirical analytic potentials with standard

parameters.

Reinhard Schinke: Global potential energy surfaces have been constructed, for the bound-state spectroscopy and dissociation of small polyatomic molecules, from high-level ab initio calculations. These surfaces have been used in full-dimensional quantum calculations to make qualitative

comparisons with experiment. Calculations and comparisons with experiment were presented for the spectroscopy of HCP and DCP, and HNO and HNCO photodissociation.

Stephen J. Klippenstein: The VRC/VTST approach for calculating rate constants for barrierless association reactions was described. Ab initio calculations are used directly in the calculations of sums of states and partition functions, by Monte Carlo averaging. Comparisons were made

between experiment and theory for different reactions.

Mark A. Johnson: A novel experimental approach was described for forming ion-molecule intermediates, whose chemical dynamics may then be probed by selective vibrational excitation. The ion-molecule system is first stabilized in an argon cluster and then the argon atoms are "boiled-off"

by exciting vibrational resonances of the ion-molecule component of the cluster. The specific cases discussed included proton transfer and SN2 nucleophilic substitution.

Sergei Skokov: Quantum calculations were discussed of the vibrational spectroscopy and unimolecular dissociation dynamics of HOCl. The quantum calculations are based on high-level ab initio calculations of the HOCl potential energy surface. This work is in part motivated by recent

experiments by Sinha which show orders of magnitude state specificity in the unimoleuclar rate constants for HOCl. The quantum calculations show that rotational coupling is an important for the state selectivity observed in the experiments.

Marsha I. Lester: Experimental studies of the spectroscopy and dynamics of the OH-H2 and OH-CH4 van der Waals complexes were described. These complexes lie in the entrance channels of the OH + H2 ---> H2O + H and OH + CH4 ---> H2O + CH3 bimolecular reactions. Studying the dynamics of these complexes is an important way to unravel the underlying dynamics of the

bimolecular reactions.

Roger E. Miller: Solvent-mediated intermolecular interactions, in clusters of liquid helium, provide a new way to prepare van-der Waals complexes in structures different than their potential energy minima. The solvent interactions give rise to potential of mean force reaction paths which

lead associating molecules into high energy van der Waals potential energy minima. These minima are then stabilized by the presence of the solvent. This approach provides a new way to determine structures of novel van der Waals complexes and to study their interactions with the solvent.

Robert W. Field: High-resolution spectroscopy is used to study vibrational states of acetylene near the acetylene <---> vinylidene isomerization threshold. The experiments are interpreted with both quantum and classical model Hamiltonians. Quasiperiodic vibrational states with regular, and non chaotic, wave-functions are found at these high energies. The experiments seem to explain another experimental observation that vinylidene is long-lived and does not decay into the rather dense continuum of acetylene vibrational states.

Kevin K. Lehmann: An experimental approach was described for exciting specific vibrational states of molecules with more than 4 eV of energy. The application of this method to HCN was reported. With this experimental technique, one can now extend studies of unimolecular dynamics to very

high vibrational energy molecular states and connect with experiments at intermediate energies.

Jaan Laane: Far-infrared, Raman, electronic absorption, and LIF spectra were used to determine the two-dimensional potential energy surfaces for the ring-puckering and ring-flapping vibrations of indan, phthalan, coumaran, and 1,3-benzodioxole in their ground and first-excited singlet

states. Important differences are found between the potential energy surfaces for the different molecules, and between the potential energy surfaces of the two electronic states for a single molecule.

Anne Myers Kelley: A resonance Raman intensity analysis was presented of the two strongly overlapping charge-transfer transitions of the carbazole/tetracyanoetylene donor-acceptor complex in solution. Modeling of the experiments yields the relative signs as well as the magnitude of the normal mode displacements in each state. It is also possible to partition the reorganization energy between the different possible contributors.

Martin P. Head-Gordon: Most modern electronic structure theory methods have been developed to provide accurate information about molecules near their potential energy minima. These methods often give a very poor description of bond breaking processes. Several examples were given of the

failure of some current methods and new general approaches were described for calculating accurate bond-rupture potential energy surfaces.

Krishnan Raghavachari: The oxidation of silicon surfaces has been studied with accurate quantum chemical calculations using cluster models. The results of these calculations provide a unifying interpretation of experimental studies of silicon oxidation, which were thought to be in conflict.

David Dixon: Developments in coupled cluster theory, combined with a family of basis sets that systematically converge to the complete basis set limit, has lead to remarkable advances in the quantitative calculation of molecular potential energy surfaces. This talk reviewed the calculation

of such potential energy surfaces as well as recent result using less computationally intensive perturbation theory methods to approximate the basis set dependence of coupled cluster methods.

Dennis R. Salahub: Recent progress was reviewed in using DFT to calculate activation energies and in performing DFT direct dynamics simulations. The specific areas of application discussed were: 1) cooperativity in networks of hydrogen bonds; 2) DFT direct dynamics of the alanine dipeptide; and 3) transition states for Fe(C2H2)+.

James C. Weisshaar: The proton NMR spectrum of alanine dipeptide (Ac-L-Ala-NHMe) dissolved in a water-based liquid crystal of cesium pentadecafluorooctanoate yields nine proton-proton dipolar couplings accurate to =B10.2 Hz. All nine couplings are fit within experimental

error by a single conformation PII (phi =3D -90 deg, psi =3D +160 deg). Two types of solvation theory find this same conformation to be lowest in energy: an ab initio electronic structure calculation with four explicit water molecules in an Onsager cavity and a molecular

dynamics simulation using the TIP3P and CHARMM22 model potentials. Evidently hydrogen bonding water bridges alter the conformational preference from the gas phase minima.

 

Michel Dupuis: The effects of solvent molecules on the electronic structure and reactivity of a solute system in activated and non-adiabatic processes was discussed. The use of a method combining direct ab initio molecular dynamics (MD) and a hybrid QM/MM-pol-vib/CONT model of the quantum molecular solute interacting with nonpolarizable or polarizable water molecules embedded in a dielectric continuum was described. Two examples were highlighted. A micro-solvated study of the SN2 type II hydrolysis reaction of CH3Cl + H2O revealed the active role of solvent molecules in concerted proton relays. Preliminary results about the non-equilibrium solvation of formaldehyde 1(n* p*) and its solvatochromic shift with QM = CAS and MR MP2) were also nted. Only one water molecule is found to have a strong H-bond interaction with H2CO in both the ground and excited states. The relaxation dynamics upon excitation was found to be dominated by large the C-O stretching and CH2 out-of-plane bending modes.

Emily A. Carter: The use of complete active space self-consistent field (CASSCF) ab initio theory in ab initio direct dynamics was described. The direct dynamics approach circumvents the need for constructing an analytic potential energy function for the molecular system under study. With

current computer power, CASSCF direct dynamics is possible for systems containing up to 20 atoms. A review of applications of CASSCF direct dynamics was given, as well as the presentation of new, exciting direct dynamics for acetylene <---> vinylidene isomerization (see above talk by Bob Field)

H. Bernhard Schlegel: Born-Oppenheimer direct dynamics is becoming a more practical approach for simulating molecular dynamics and chemical reaction dynamics. Approaches for optimizing the solution of the classical equations of motion for such simulations were discussed. The number of

electronic structure calculations of energies, gradients, and force constants needed to perform these simulations can be significantly reduced by using local quadratic expansions on the potential energy surface, with predictor-corrector integration, and using hessian updates. Such

improvements in the numerical algorithms makes the direct dynamics simulation substantially more efficient and extends this approach to larger molecular systems and/or longer time frames.

Todd J. Martinez: In recent work ab initio multiple spawning and related methods have been developed, which couple ab initio direct dynamics with the solution of the nuclear Schroedinger equation at various levels of theory. Progress in this approach and applications to chemical reactions involving tunneling and multiple electronic states were discussed. The accuracy of the simulations were judged by comparisons with experiment.

Gustavo E. Scuseria: This talk presented recent developments in linear scaling electronic structure methods including density functional, MP2, and coupled cluster theories. Using atomic orbital formulations, linear scaling with molecular size has been demonstrated for both DFT and wave

function methods. The talk focused on issues regarding the trade-off between accuracy and speed.

Gilles H. Peslherbe: Semiempirical direct dynamics simulations were used to study the scattering of high velocity molecular and atomic clusters off hard surfaces. The systems simulated included the surface-induced reactions of nitrogen clusters and buckeyball fragmentation.

Peter Pulay: Ab inito direct dynamics simulations are usually performed using a Hamiltonian with Cartesian coordinates and momenta. The use of an internal coordinate Hamiltonian is also possible and, for some specific applications the ab initio direct dynamics may be more efficient in this

coordinate representation than in Cartesians.

 

Conference Announcements

Future ACS Meetings

Washington, DC, Aug. 20-25, 2000

Program Chair: Daniel Neumark, Department of Chemistry, University of California, Berkeley, CA 94720, (510)642-3502 FAX (510)642-6262, email: dan@radon.cchem.berkeley.edu

San Diego, CA, April 1-5, 2001

Program Chair: Professor Richard Stratt, Department of Chemistry, Brown University, 324 Brook Street, Providence, RI 02912, richard_stratt@brown.edu

Chicago, IL, August 26-30, 2001

Program Chair: Professor Richard Stratt, Department of Chemistry, Brown University, 324 Brook Street, Providence, RI 02912, richard_stratt@brown.edu

Orlando, FL, April 7-11, 2002

Program Chair: Professor John C. Hemminger, Department of Chemistry, University of California, Irvine, CA 92697, jchemmin@uci.edu

Boston, MA, September 8-12, 2002

Program Chair: Professor John C. Hemminger, Department of Chemistry, University of California, Irvine, CA 92697, jchemmin@uci.edu

 

2002 ACTC: American Conference on Theoretical Chemistry

Organizer: Kenneth D. Jordan

Planned location: Seven Springs Mountain Resort, Champion, PA 15622

Planned dates: July 13 - 18, 2002 http://www.pitt.edu/~jordan/actc/

 

 

 

 

 

 

 

 

 

 

Subdivision Officers

Current Officers

 

Chair

Professor Kenneth Jordan

Department of Chemistry

University of Pittsburgh

Pittsburgh, PA 15260

 

Chair-Elect

(Program Chair for 2000,

Subdivision Chair for 2001)

Professor Susan Tucker

Department of Chemistry

University of California, Davis

Davis, CA 95616

Vice Chair

(Program Chair for 2001,

Subdivision Chair for 2002)

Professor Edwin L. Sibert

Department of Chemistry

University of Wisconsin

Madison, WI

Secretary

Professor Michael Page

Department of Chemistry

North Dakota State University

Fargo, North Dakota 58105

Council of Past Officers

Professor Rodney Bartlett

University of Florida

Professor Bruce Berne

Columbia University

Professor Joel M. Bowman

Emory University

Professor David Chandler

University of California, Berkeley

Dr. Ralph Christofferson

The Upjohn Company, Kalamazoo

Professor J. T. Hynes

University of Colorado

Professor Mark Gordon

Iowa State University

Professor Joyce Kaufman

Johns Hopkins University

Professor Philip Pechukas

Columbia University

Professor William P. Reinhardt

University of Washington

Professor Stuart Rice

University of Chicago

Professor H. F. Schaefer

University of Georgia

Professor George C. Schatz

Northwestern University

Professor Isaiah Shavitt

Ohio State University

Professor Jack Simons

University of Utah

Professor Donald G. Truhlar

University of Minnesota

Dr. John C. Tully

AT&T Bell Laboratories

Prof. John D. Weeks

University of Maryland

Professor Benjamin Widom

Cornell University

Professor Robert Wyatt

University of Texas at Austin

Professor William L Hase

Wayne State University

Professor Jim Skinner

University of Wisconsin

Prof. David R. Yarkony

Johns Hopkins University

Professor Rich Stratt

Brown University