Basic Energy Sciences
Quantum Chemistry and Reaction
Dynamics
Jeff Nichols, Deputy Director
WR Wiley Environmental Molecular Sciences Laboratory
Pacific Northwest National Laboratory
Richland, WA 99352
Dr. Robert J. Harrison, Pacific Northwest National Laboratory
Dr. Martin Head

Gordon, Lawrence Berkeley National Laboratory
Dr. Mark S. Gordon, Ames Laboratory
Professor Piotr Piecuch, Michigan State University
Professor Peter R. Taylor, University of California, San Diego
Professor Henry Frederick Schaefer III, University of Georgia
Professor Gustavo E. Scuseria, Rice University
Professor Russ Pitzer, The Ohio State University
Dr. Walter C. Ermler, Program Director for Research, EHR/REC
Dr. Albert F. Wagner, Argonne National Laboratory
Professor Donald L. Thompson, Oklahoma State University
QC
RD
Basic Energy Sciences
Some Collaborations Have Already Been
Established
Ames, MSU
PNNL, LBNL,
UGA, UCSD
OkSU
ANL
UMd
SNL
Rice
OSU, U of Mem
ISICs
Colaboratory Pilot (CMCS)
Basic Energy Sciences
Advanced Methods for Electronic Structure
Robert J. Harrison and Jeff Nichols, PI
•
Collaborators
–
GI Fann, E Apra, PNNL
–
G Beylkin, U Colorado
–
HF Schaefer, III, UGA
–
PR Taylor, UCSD/U Warwick
–
M Head

Gordon, LBNL
One of three complementary projects:
•
Sandia National Laboratory,
“A Computational Facility for Reacting Flow Science,”
and
•
Argonne National Laboratory,
“Advanced Software for the Calculation of Thermochemistry,
Kinetics, and Dynamics.”
to address electronic structure, chemical kinetics, and fluid mechanics issues necessary to create a software
revolution in the simulation of chemically reacting turbulent flows. To the degree that funding allows, our
intention is to initiate a collaboration that will grow over time into a coordinated software development
program.
Basic Energy Sciences
A Multiresolution Approach to Quantum Chemistry in
Multiwavelet Bases
•
Complete elimination of the basis error
–
One

electron models (HF, DFT), pair models (e.g., MP2, CCSD)
•
Correct scaling of cost with system size
•
General approach
–
readily accessible by students, small computer code
•
Potential impact similar to the FFT on physics
•
Realizable numerical algebraic regularization
•
Faster algorithms with separable representation of kernels for integro

differential
equations
•
Applications to other domains including atmospheric dynamics and materials
Robert J. Harrison and G.I. Fann
Gregory Beylkin
Pacific Northwest National Laboratory
University of Colorado
Basic Energy Sciences
A Multiresolution Approach to Quantum Chemistry in
Multiwavelet Bases
Harrison, Fann and Beylkin
•
Distinguishing features
–
Multiresolution analysis in multiwavelet bases
–
Disjoint
intervals efficiently adapt to singularities
–
Non

standard representation of functions / operators
–
Integral operators scaling as
O(Nk
4
)
or better
•
Density Functional Theory
–
Integral formulation
–
nominally no derivatives
•
Initial applications
–
Benchmark calculations on polyatomic systems
•
Connections to ISICs
–
MRA in 3

D and 6

D; visualization of 3

D and 6

D numerical functions; NUMA
programming tools; sparse matrix BLAS and linear algebra,
CCA and
performance analysis and tuning
Basic Energy Sciences
•
Grid used to represent the nuclear
potential for H
2
using k=7 to a
precision of 10

5
.
•
Automatically adapts
–
it does not
know a priori where the nuclei are.
•
Nuclei at dyadic points on level 5
–
refinement stops at level 8
•
If were at non

dyadic points
refinement continues (to level ~12) but
the precision is still guaranteed.
•
In future will dyadically refine with
various lengths to force nuclei to box
corners.
A Multiresolution Approach to Quantum Chemistry in
Multiwavelet Bases
Harrison, Fann and Beylkin
Basic Energy Sciences
Accurate Properties for Open

Shell States of Large Molecules
Peter R. Taylor, UCSD/ U. Warwick
Objectives
•
Extend the applicability of accurate, reliable chemical
predictions for closed

shell molecules to radicals, excited
states, and situations in which chemical bonds are broken
•
Develop response methods for calculating properties for
these systems
•
Improve convergence of results by exploiting two

particle
basis functions
•
Extend this approach to systems with dozens of open

shell
electrons
Basic Energy Sciences
Accurate Properties for Open

Shell States of Large Molecules
Peter R. Taylor, UCSD/ U. Warwick
Approach
•
Implement scalable CASPT2 energies and response
properties (new software)
•
Integrate existing work on CASPT2 using two

particle
basis functions (existing software)
•
Develop and implement group function approach for
weakly coupled open

shell sites such as polynuclear
transition

metal complexes or ferredoxins (new equations,
new algorithms, new software)
Basic Energy Sciences
Development of Next

Generation, Explicitly

Correlated
Electronic Structure Methods for Sub

Chemical Accuracy
Fritz Schaefer, University of Georgia
•
New closed

shell, integral

direct MP
n

R12 and CC
n

R12 codes are being created to
take advantage of our recently developed integrals package CINTS. Our MP2

R12
work has already provided the scientific community explicitly

correlated methodologies
for workstation computations with as many as 1500 basis functions and essentially no
angular momentum limits, at least through
k
functions.
•
The
full
promise
of
R
12
methods
is
being
pursued
by
further
development
of
evaluation
methods
for
many

electron
integrals
.
Through
demanding
computations
with
enormous
basis
sets,
deficiencies
in
the
standard
approximations
of
R
12
theory
are
being
identified
and
understood
.
Improvements,
such
as
dual
basis
set
schemes,
are
being
investigated
for
better
completeness
insertions,
particularly
ones
with
improved
consistency
over
broad
regions
of
potential
energy
hypersurfaces
.
•
For
combustion
and
atmospheric
chemistry
applications,
we
plan
critical
development
and
implementation
of
explicitly

correlated
(R
12
)
open

shell
perturbation
and
coupled

cluster
theories,
both
within
less
complicated
unrestricted
(UHF)
formalisms
and
more
difficult
spin

adapted
(ROHF)
approaches
.
Basic Energy Sciences
Local Correlation
Martin Head

Gordon, LBNL
•
Coupled cluster
(CC) methods are the
most accurate
quantum chemistry
methods in wide use.
–
They are accurate for reaction barriers where simpler density functional
theory (DFT) methods often fail.
•
But
CC methods are restricted to small molecules, and are
very
computationally expensive compared to DFT.
–
Application to large molecules is blocked because cost rises with the 6
th
and 7
th
powers of molecular size.
•
Thus immediate development of parallel algorithms is
not
going to
permit application to larger molecules.
•
Goal:
develop alternative formulations of CC theory which reduce the
cost scaling to quadratic or linear with molecular size, without
destroying accuracy.
Basic Energy Sciences
Local Correlation

Overview of Planned Work
Martin Head

Gordon, LBNL
•
Our reduced scaling CC methods must permit:
–
Continuous potential surfaces.
–
Viability with large basis sets.
–
Both energies and forces must be available.
•
We’ve defined a new ansatz that reduces the number of CC variables to
quadratic, and satisfies the above criteria.
–
The accuracy of this ansatz must be established
•
We’ll avoid the difficulty of very large basis sets by combining our CC
methods with a density functional style correlation functional.
–
The performance of this hybrid approach must be tested.
•
Serial code will be developed for testing and refinement.
•
When results justify it, parallel algorithms will be pursued in
collaboration with the NWChem team.
Basic Energy Sciences
Computational Chemistry
Mark Gordon, Ames Laboratory
Participants:
•
Mark Gordon
•
Mike Schmidt
•
Klaus Ruedenberg
•
James Evans
Collaborators:
•
Piotr Piecuch (Michigan
State)
•
Don Truhlar (Minnesota)
•
Scalable Computing Lab:
Ames Lab
•
PNNL
Basic Energy Sciences
Computational Chemistry
–
Objectives for Highly Accurate
Quantum Chemistry Codes 1
Mark Gordon, Ames Laboratory
•
Full Configuration Interaction (Full CI)
–
Exact wavefunction for a given atomic basis
–
Serves as benchmark for approximate correlated methods:
–
Currently limited to modest basis sets, atoms, very small molecules
–
Need scalable code to apply Full CI more broadly
–
Replicated data algorithm: limited molecular size
–
Distributed data algorithm: communication issues
–
Programming Models interface: Data compression (Kendall)
•
Scalable General CI
–
Full CI limited in scope
–
Most truncated CI based on “full space”
ansatz
–
Extend scope of CI by eliminating “deadwood”: only include
important configurations
Basic Energy Sciences
Computational Chemistry
–
Objectives for Highly Accurate
Quantum Chemistry Codes 2
Mark Gordon, Ames Laboratory
•
Scalable MCSCF
–
Frequently require orbitals optimized in CI space
–
More demanding than CI
–
Most common MCSCF implementation: FORS/CAS
•
Expand Accessible MCSCF Active Space
–
MCSCF based on General CI: eliminating deadwood
–
Q

CAS based on localized orbitals
•
Efficient Scalable Coupled Cluster Methods: Piecuch
•
Open Shell Perturbation Theory Gradients
Basic Energy Sciences
Computational Chemistry
–
Objectives for Spanning Multiple
Time and Length Scales
Mark Gordon, Ames Laboratory
•
Scalable Kinetic Monte Carlo Codes with Focus on
Surface Phenomena
•
Develop New Integrated Atomistic & Mesoscale
Descriptions of Surface Phenomena
–
Pattern formation in catalytic surface reactions
–
Nanostructure evolution during surface processes
•
Chemical vapor deposition (CVD)
•
Etching of semiconductor surfaces
•
Heterogeneous catalysis
•
Interface with continuum mesoscale modeling
Basic Energy Sciences
The “holy grail” of the
ab initio
electronic structure theory:
The development of
simple
,
black

box
, and
affordable
methods that can provide
highly
accurate
(~spectroscopic) description of
ground

and excited

state potential energy
surfaces
New Coupled

Cluster Methods For Molecular Potential
Energy Surfaces
Piotr Piecuch, Michigan State University
Examples of applications:
•
dynamics of reactive collisions
•
highly excited and metastable ro

vibrational states of molecules
•
rate constant calculations
•
collisional quenching of electronically
excited molecular species
Motivation:
•
elementary processes that occur in
combustion (e.g., reactions involving OH
and N
x
O
y
)
•
collisional quenching of the OH and
other radical species
Basic Energy Sciences
New Coupled

Cluster Methods For Molecular Potential
Energy Surfaces

Specific Goals
Piotr Piecuch, Michigan State University
•
New CC methods for ground

state potential energy
surfaces:
–
method of moments of CC equations
–
renormalized CC approaches
•
New CC methods for excited

state potential energy
surfaces:
–
method of moments of CC equations
–
active

space EOMCC approaches
MBPT(2)

like choices of
lead to the renormalized and completely
renormalized CCSD(T), CCSD(TQ), CCSDT(Q), etc. approaches
Basic Energy Sciences
New Coupled

Cluster Methods For Molecular Potential
Energy Surfaces
–
Future Work
Piotr Piecuch, Michigan State University
•
Methods and algorithms

ground

state problem
–
Incorporation of the renormalized CCSD(T), CCSD(TQ), and CCSDT(Q) methods in GAMESS
–
Development of the MMCC schemes with the non

perturbative choices of
–
Extensions of the MMCC and renormalized CC methods to open

shell states and reference configurations of the
ROHF type
–
Work with Professor Mark S. Gordon and coworkers on parallelizing the MMCC and renormalized CC methods
within GAMESS
•
Methods and algorithms

excited

state problem
–
Extension of the MMCC theory to the MMCC(2,4) case and extension of the active

space EOMCC theory to the
EOMCCSDtq case
–
Development of efficient computer codes for the MMCC and active

space EOMCC methods and incorporation of
these codes in GAMESS
–
Development of the MMCC and active

space EOMCC methods for non

singlet states and formulation of the EA and
IP extensions of the active

space EOMCC approaches
–
Extension of the active

space EOMCC approaches to properties other than energy
–
Development of the MMCC schemes with the perturbative choices of
(renormalized EOMCCSD(T) method ?)
–
Work with Professor Mark S. Gordon and coworkers on parallelizing the excited

state MMCC codes within
GAMESS
Basic Energy Sciences
Quantum Chemistry for Periodic Systems
Gustavo E. Scuseria, Rice University
•
Objectives
–
To develop methods and computational programs for the
accurate
prediction of
electronic
and
optical
properties of polymers, surfaces, and solids with large unit
cells
–
Applications to
polymers
and
catalysis
•
Approach
–
Use Gaussian orbitals for across the Periodic Table
reliability
–
Use Fast

Multipole Methods for achieving
linear scaling
in the Coulomb problem
–
Fast quadratures and alternatives to diagonalization for O(N) performance
–
Develop
better
DFT functionals for increased
accuracy
•
Payoffs
–
Increase capabilities for
modeling
materials and processes
–
Big
impact
on areas where quantum molecular modeling is routinely used:
chemical, pharmaceutical, and defense industries
–
Incorporation to
Gaussian
package
Order (N) tools for Periodic Systems
Basic Energy Sciences
Relativistic Multireference Quantum Chemistry
R. M. Pitzer, B. E. Bursten, I. Shavitt
Ohio State University
•
Strengths
–
Includes relativistic effects
–
Describes complicated electron coupling
–
Includes electron correlation
•
Needs
–
Extensive testing and tuning of recent parallel version
–
More flexible core potentials (W. C. Ermler)
–
Parallel versions of ancillary programs
–
Refinement of diagonalization algorithm
•
Applications
–
Actinide complexes in solution and on surfaces
–
Lanthanide intensities in crystals
Basic Energy Sciences
Reliable Electronic Structure Calculations for Heavy Element
Chemistry: Molecules Containing Actinides, Lanthanides,
and Transition Metals
W. C. Ermler and M. M. Marino, Department of Chemistry, The
University of Memphis
Relativistic Pseudopotentionals (RPPs)
•
RPPs are based on extending the usual two

space representation of atomic electrons
(core and valence) to three spaces (core/outer core/valence).
•
The RPP has embedded within it the standard small

core RECP that relegates the outer
core electrons to the valence space.
•
The RPP is ultimately calculated in its entirety at runtime and is specific to the
molecular geometry and electronic state.
•
Only the smallest numbers of molecular valence electrons need to be treated explicitly.
•
The RPP can be used in any treatment of the electronic structure [DFT, CI, CCSD(T),
etc.]
Small

core RECPs embedded within very

large

core RPPs, in conjunction with advanced computing platforms, permit the
highly accurate ab initio treatment (including correlation, outer

core/valence polarization, and spin

orbit coupling) of
systems possessing orders of magnitude more electrons than are tractable using current codes and platforms.
Basic Energy Sciences
Advanced Software for the Calculation of Thermochemistry,
Kinetics and Dynamics

Parallelization of Cumulative
Reaction Probabilities (CRP)
Al Wagner, ANL
•
computationally intensive core of reaction rate constants
•
mathematical kernel
(all matrices are sparse with some structure):

method 1:

iterative eigensolve (imbedded iterative linearsolves)

clever preconditioning important

portability based on ANL PETSc library of kernels

method 2:

Chebyschev propagation (=> matrix vector multiplies)

novel finite difference representation (helps parallelize)
•
programing issues
:

parallelization

exploiting data structure (i.e., preconditioning)
Basic Energy Sciences
Advanced Software for the Calculation of Thermochemistry,
Kinetics and Dynamics

Parallel Implementation of Subspace
Projection Approximate Matrix (SPAM) method
Al Wagner, ANL
•
novel iterative method to solve general matrix equations

eigensolve

linear solve

nonlinear solve
•
applications are widespread
–
in chemistry: CRP, electronic structure (SCF, MRSDCI,…)
•
mathematical kernel
:
–
related to Davidson, multigrid, and conjugate gradient methods
–
subspace reduction (requiring usual matrix vector multiplies)
–
projection operator decomposition of matrix vector product
–
substitution of user

supplied approximate matrix in computationally
intensive part of decomposition
–
sequence of approx. matrices => multilevel method
•
programing issues
:
–
generalization of approach (only done for eigensolve)
–
incorporation into libraries (connected to TOPS project at ANL)
–
test of efficacy in realistic applications (e.g., CRP)
Basic Energy Sciences
Theoretical Chemical Dynamics of Elementary Combustion
Reactions
Don Thompson, Oklahoma State University
1. Potential Energy Surfaces
We are developing methods for direct use of ab initio energies and forces in dynamics
simulations based on interpolating moving least

squares. The method can be used to
generate global representations for dynamics calculations. It can also be integrated into
direct (on

the

fly) dynamics simulations, providing a means of reducing the
computation expense by using interpolation. Furthermore, we will attempt to develop
methods for "on the fly scaling" of values so that lower

level quantum methods can be
used.
Note: The interpolating moving least

squares method requires the determination of
optimum polynomial expansion coefficients. The extension of this approach to large
numbers of atoms will be made practical by the using parallel computing.
Project goal: Development of methods and software for more accurate and efficient
simulations and rate calculations for complex chemical reactions involving large
polyatomic molecules and radicals.
Basic Energy Sciences
Theoretical Chemical Dynamics of Elementary Combustion
Reactions
Don Thompson, Oklahoma State University
2. Molecular Dynamics Simulations and Rate Calculations
The treatment of the dynamics of reactions involving polyatomic
molecules presents a challenging problem since they often involve
quantum effects, yet quantum mechanical methods are not capable of
treating more than a few atoms.
We are developing quasiclassical and
semiclassical methods for practical dynamics simulations of complex
reactions in large molecules.
We are developing a general computer code
that implements these methods and that incorporates various ways of
representing the potential, including the direct use of ab initio forces. The
size of problems that can be treated can be greatly increased by taking
advantage of many processors to compute the large ensembles of
trajectories needed to determine rates and other dynamical properties of a
system.
Basic Energy Sciences
Basic Energy Sciences
Basic Energy Sciences
Enter the password to open this PDF file:
File name:

File size:

Title:

Author:

Subject:

Keywords:

Creation Date:

Modification Date:

Creator:

PDF Producer:

PDF Version:

Page Count:

Preparing document for printing…
0%
Σχόλια 0
Συνδεθείτε για να κοινοποιήσετε σχόλιο