Highly Parallelized Large Scale Atomistic Simulations for Design of Materials

NSF-GCAG (ASC 9217368) 1994 REPORT

Contents

Introduction
Organization
Title of Effort
Objective
Principal Investigators
Related Information

Approach

[Quantum Mechanics] [Force Fields] [Molecular Dynamics]
[Coarse Graining] [Statistical Mechanics] [Continuum Parameters]

Progress

[QM-Finite] [QM-Infinite] [Dynamics-KSR] [Dynamics-Intel]
[Dynamics-NEIMO] [Statistical Mechanics-GCMC]

Recent Accomplishments

Significant Events and Accomplishments

Prediction of Glass Temperature of Polymers
Quantum Mechanics of Large Finite Molecules
Nonlinear Optical Materials
Chemical Properties of Solid Surfaces

Fiscal '95 Plan

Technology Transition


INTRODUCTION

Organization

Materials and Process Simulation Center,
Beckman Institute,
California Institute of Technology

Title of the Effort

Highly Parallelized Large Scale Atomistic Simulations for Design of Materials

Objective

The objective is to develop theoretical methodologies for practical computations of the structures and properties of real materials that can be used in industrial process design for manufacturing new materials.

Principal Investigators

William A. Goddard III, wag@wag.caltech.edu
Department of Chemistry, Beckman Institute (139-74),
Caltech, Pasadena, CA 91125

Richard Friesner, rich@cucbs.chem.columbia.edu
Department of Chemistry, Columbia University, New York, NY 10027

Zhen-Gang Wang, zgw@macpost.caltech.edu
Department of Chemical Engineering (210-41),
Caltech, Pasadena, CA 91125

Abhinandan Jain, jain@telerobotics.jpl.nasa.gov
Robotics, Jet Propulsion Laboratory (198-219),
Pasadena, CA 91109

Stephen Taylor, steve@cs.caltech.edu
Department of Computer Science (256-80),
Caltech, Pasadena, CA 91125

Related Information

The full 1994 report of the Materials and Molecular Simulation Center in the Beckman Institute at Caltech is also available on the World Wide Web (WWW). This report includes the detailed progress reports on the NSF-GCAG project along with projects supported by other agencies and by seven industrial collaborators.

APPROACH

There is an enormous gap between current methodologies for atomistic simulations and the level required for accurately describing the relevant properties of industrially important materials. Our strategy is to transcend from the most fundamental theory (quantum mechanics, QM) to practical engineering designs in a sequence of four or five levels as indicated in the following figure.

Figure 1. Hierarchy of Models for Simulation.

Modeling Hierarchy


PROGRESS

Our team of 5 PI's has made significant progress on each of the six tasks described under APPROACH. We have developed new theoretical methods for quantum mechanics and molecular dynamics that scale sufficiently slowly with size so as to be practical for the very large systems of industrial interest. We are well along in parallelizing these methods for optimal performance on highly parallel high performance computers.

RECENT ACCOMPLISHMENTS


SIGNIFICANT EVENTS AND ACCOMPLISHMENTS

  1. PREDICTION OF GLASS TEMPERATURES OF POLYMERS.
    A key, potentially very significant industrial application for atomistic simulations is the prediction of glass temperatures, T_g. Above T_g the polymer is soft and can be formed or extruded; below T_g it is stiff. Industry would like to tune the glass temperature and the modulus to attain desired values by alloying the polymer with different monomers (forming copolymers), by cross linking, by blending or by using additives. Currently this is done empirically leading to costly and wasteful experiments. If theory could be used to predict the best choices there is the potential for considerably reducing the number of such experiments. Using the new MD techniques developed under the GCAG and working with industrial collaborators (Chevron, BF Goodrich, Asahi Glass), we have demonstrated (for eight cases) excellent predictions of the glass temperature. The simulations predict a glass temperature of 396K for teflon in good agreement with the experimental value of 400K. Equally exciting, analysis of the simulations explain the underlying phenomena controlling the glass temperature. Namely it is the point above which gauche-trans transformations compete with diffusion. Such concepts may allow new applications for rapid prediction of how the glass temperature is modified by changing the material (carrying out large scale calculations only for selected cases).

  2. QUANTUM MECHANICS OF LARGE FINITE MOLECULES.
    We have developed a new methodology (PS-GVB) combining pseudospectral (PS) multi-grid and dealiasing strategies with sophisticated many-body wavefunctions [e.g., generalized valence bond (GVB)]. PS-GVB has been extended to treat all atoms of the periodic table. This combined a valence bond formulation for estimating initial guesses of wavefunctions, core effective potentials to treat the core electrons, and new grid and dealiasing functions. These methods scale with size as N^2 (rather than the N^3 of standard programs) and are 10 to 100 times faster than standard programs (depending on size). The PS-GVB method has been extended to treat solvation effects self-consistently using dielectric continuum methods, a Poisson-Boltzmann solver, and a self-consistent reaction field method. Like DelPhi, PS-GVB's Poisson-Boltzmann solver uses a cavity based on the real molecular surface, rather than the spherical cavity used by other programs. PS-GVB has been extended to calculate hyperpolarizabilities and applied to the new high-beta NLO organics. Second-order Moller-Plesset perturbation theory (MP2) has been implemented into PS-GVB, leading to improvements by a factor of 10 to 100, depending on size of the system. Licenses of this technology from Caltech and Columbia to Schrodinger Inc. have been arranged. Schrodinger has added a user-friendly interface and extended the program in many ways. On October 15, 1994 the first full commercial release will be made. It is anticipated that in two years PS-GVB will be in use at 100 US industrial sites plus 100 US university sites.

  3. NONLINEAR OPTICAL MATERIALS.
    We have developed a simple valence bond theory (VB-CT) for predicting the trends in nonlinear optical properties (hyperpolarization) of new organic materials as a function of donor, acceptor, linker length, and solvent. VB-CT provides a way for experimentalists to quickly select the proper combination to maximize the various hyperpolarizabilities. This theory explains the derivative relationship of various polarizabilities observed experimentally for these materials. Using PS-GVB we have now succeeded in accurately predicting the hyperpolarizabilities of the newest extremely high hyperpolarizability materials, thus confirming both the experiment and the simple theory.

  4. QUANTUM MECHANICS OF CHEMICAL PROPERTIES ON SOLID SURFACES.
    We have developed and tested a new methodology for predicting the chemical properties at surfaces and interfaces which should be useful in optimizing thin film growth. This methodology, GDS-DFT, extends density functional theory to use of Gaussian type functions by using a dual space strategy. This has been tested successfully on CdTe(100), HgTe(100), GaAs(110), and is being used in two industrial projects (HgCdTe with Hughes, corrosion inhibitors with Chevron).

FY-95 PLANS


TECHNOLOGY TRANSITION

Schrodinger Inc., Pasadena CA (contact Dr. Murco Ringnalda, ph: 818-568-9392, fax: 818-568-9778, email: info@psgvb.com) has licensed the PS-GVB technology from Caltech and Columbia. They have added a user-friendly interface, extensive user guide, and extended the program in many ways. On October 15, 1994 the first full commercial release will be made. It is anticipated that in two years PS-GVB will be in use at 100 US industrial sites plus 100 US university sites.

Chevron Petroleum Technology Co., La Habra, CA (Dr. Yongchun Tang, ph: 310-694-7550) uses PS-GVB, GDS-DFT, and MD-CMM to design new scale inhibitors and corrosion inhibitors for oil recovery applications (designing new and more effective calculations).

Allied-Signal, Morristown, NJ (Dr. Willis Hammond, ph: 201-455-4914) uses MD-CMM to predict structure and moduli of nylon polymers.

Hughes Research Labs., Malibu, CA (Dr. Jenna Zinck, ph: 310-317-5913) uses GDS-DFT to design metallorganics for MO-MBE deposition of HgCdTe single crystal films.

DATE PROPOSAL: September 20, 1994


Last modified on September 26, 1995.
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