Information Technology Laboratory, Applied and Computational Mathematics Division
NIST only participates in the February and August reviews.
The solution of the time dependent Schroedinger equation for many-electron atoms and molecules exposed to electromagnetic radiation presents a formidable problem both conceptually and computationally. A group of researchers at Kennesaw State University, the University of Central Florida, Aarhus University in Denmark, and NIST have been developing quite sophisticated computational approaches to treating "small" atomic and molecular systems exposed to short, intense laser radiation. Our approach marries the most advanced quantum chemistry methods at short range with finite element methods at long range to produce optimal representations over all space. Extracting quantitative results has necessitated the development of sophisticated algorithms and requires large-scale calculations on supercomputers. The methods developed are state-of-the-art and the computer codes are algorithmically designed to scale efficiently to many thousands of processors. They have been applied to a number of one, two, and many electron atoms and molecules to extract single and double ionization probabilities. To date, the calculations have revealed numerous interesting and unexpected features, in single and double ionization processes that are among the first of their kind.
We are expanding the scope of our work in several ways. These include the development of better, more accurate, grid based, multi-center quadratures to treat hybrid basis sets, new time propagation algorithms and density-functional-based methods that are needed to quantitatively model dynamical processes in very large molecular systems.
The group currently has a number of NSF awards and has successfully competed for computational resources on the eXtreme Science and Engineering Discovery Environment project. An Associate joining the project will have access to the most sophisticated and powerful computers in the world and will also get to collaborate with a world class group of theoretical and computational physicists.
References
Schneider B. I., et al: Advances in Chemical Physics 157: John. Wiley & Sons, Inc
Feist J, et al: Physical Review Letters 103: 063002, 2009
Guan X, et al: Physical Review A 88: 043402, 2013
Guan X, et al: Physical Review A 90: 043416, 2014
N. Douguet, B. I. Schneider, and L. Argenti, Application of the Complex Kohn Variational Method to Attosecond Spectroscopy, Physical Review A 98: 023403, 2018
H. Gharibnejad, B. I. Schneider, M.Leadingham and H. Schmale, A Comparison of Numerical Approaches to the Solution of the Time-Dependent Schroedinger Equation in One Dimension, Computer Physics Communications, https://www.sciencedirect.com/science/article/pii/S0010465519301778?via
H. Gharibnejad and B. I. Schneider, Numerical Methods Every Atomic and Molecular Physicist Should Know, Nature Reviews Physics, Dec, 16, 2019. NIST ITL award for best journal paper of 2019-2020
Heman Gharibnejad, Nicholas. Douguet, B. I. Schneider, Jeppe Olsen and Luca Argenti, Multi-Center Quadrature Scheme for the Molecular Continuum, Computer Physics Communications 263, 107889 (2021)
Liam H. Scarlett, Jeremy S. Savage, Dmitry V. Fursa, Igor Bray, Mark C. Zammit, and Barry I. Schneider, Convergent Close-Coupling Calculations of Electrons Scattering on Electronically Excited Molecular Hydrogen, Phys. Rev. A 103, 032802 (2021)
Quantum dynamics; Electron correlation; Computational physics; Laser-matter interaction; Density functional methods; Algorithm development;