Science
Basic science research provides the foundation for innovations to help meet the challenges in energy, environment and national security. The Science application area includes modeling and simulation in a variety of basic science areas, especially biology, chemistry and radiation. These science applications are grouped broadly as biological science, chemical science, computational methods, materials science, and nuclear science modeling and simulation.
Biological Science
Biological science applications of modeling and simulation at PNNL span the molecular to the anatomical scale. Advancement of 21st-century biology will be dominated by research at the convergence of biological, physical, and information sciences. A major challenge is the application of genomics knowledge to the understanding of biological structure and function in living systems. Systems biology research involves vast amounts of data, and new technologies are required to capture, store, access, and analyze it. Managing the huge amounts of biological data and developing new computational and statistical methods for analysis and modeling will be key to implementing a systems approach to biology.
Chemical, Geochemical, and Molecular Science
Chemical science applications of modeling and simulation at PNNL span a broad range of areas, supported by PNNL's signature strength in code development for molecular-scale simulations. PNNL staff are nationally recognized for unique capabilities in simulation of molecular and interfacial reactions, including those involving actinide species. PNNL's signature strengths include chemical transformations at complex interfaces, condensed phase and interfacial chemical physics, and computational chemistry and geochemistry. Our researchers have developed two advanced software tools to model molecular and interfacial reactions. NWChem, DOE's premier high performance parallel computational chemistry code and the Extensible Computational Chemistry Environment (Ecce) enable the modeling of large scientific problems, such as those in actinide chemistry.
PNNL has considerable modeling expertise, experience, and capabilities in characterizing radiation-induced chemistry, such as hydrogen and oxygen generation from solution and liquid- or gas-solid interfaces. Modeling combines high-level ab initio electronic structures with complex theories of reaction dynamics, both extended to the condensed phase. Experimental characterization conducted at PNNL plays an important role in the development and benchmarking of accurate models of fundamental physical processes. PNNL has developed the computer-aided molecular design software, HostDesigner, for rapidly evaluating millions of potential molecules and identifying a small number of candidates with a high probability of being effective ligands before their synthesis and testing.
Computational Performance and Methods
Computer performance modeling, development of high performance computing methods, multiscale approaches, and sensitivity and uncertainty propagations are the areas of computational methods applications of modeling and simulation at PNNL. Researchers at PNNL are developing software tools to achieve optimum performance on existing and possible high-end computer systems. Experimental data is used to estimate parameter uncertainties (distributions) as well as biases and uncertainties of models. The validation of models, i.e.,comparing model results to experimental data, requires statistical methods to account for model and data uncertainties. Due primarily to increased computational power, many techniques are evolving in sensitivity and uncertainty analysis, for example, to evaluate the validity of hydrology flow and transport of contaminates at Hanford. Several mathematical techniques are under development for propagation between physical scales and through models, such as from one process, or node, to another.
Electromagnetics and Elastic Wave Phenomena
Electromagnetics and elastic wave phenomena involve the interaction of wave phenomena with materials. The applications include nondestructive evaluation of components and structures using acoustic wave analysis, eddy-current analysis, and Terahertz imaging; simulation and design of passive and active Radio Frequency (RF) tags used for Tagging, Tracking, and Location; RF imaging for crowd scanning and portal threat detection; advanced biometric analysis and tracking; and active ultrasonic material manipulation.
A typical application will involve the modeling of a system for use with electromagnetic and/or acoustic characterization. An experimental system will then be created to demonstrate the viability of using a particular method to characterize a test object. The object is then scanned using acoustics and/or electromagnetics to detect the features desired at the outset. Typical outcomes include using low-frequency, eddy-current scanning to determine defects in metallic surfaces; ultrasonic scanning to detect strain locations within natural gas pipes; and high-frequency imaging to detect the existence of contraband (weapons, explosives, etc.) within a defined area.
A major challenge involves combining multi-domain interaction mechanisms to more accurately characterize the desired object. Such multi-domain methods combined with advanced computational methods may enable applications such as real-time biometric analysis and crowd scanning. Advancements in resolution and scanning techniques could result in devices with high resolution, low cost, and accurate subject characterization.
Materials Science and Materials Informatics
Fundamental research on materials and modeling of individual components is a major area of strength at PNNL. Examples include
- First principle solid-state calculations on materials
- Experience in development of inter-atomic potentials for metals, ceramics, glasses, and incorporated gases
- Multi-scale modeling and simulation efforts related to radiation effects, gas transport, phase stability, and microstructure evolution in materials related to nuclear fuels, advanced cladding (such as in SiC or ZrC for pebble fuels), inert matrix fuels, graphite moderators, nuclear waste glasses, nuclear waste ceramics, and structural components
- Experience in the development of Molecular Dynamics and Kinetic Monte Carlo codes for studying radiation effects and other processes at far from equilibrium conditions—PNNL has experience, expertise, and capabilities in validating models (atomistic to continuum) against experiments, including defect configurations, phase transformations, radiation damage states, and gas diffusion and radiation-induced transformation.
Researchers at PNNL have fundamental and practical experience in inspection sciences, including inspection modalities such as acoustics and ultrasound, optics, and electromagnetics. Our researchers also have capabilities in fundamental radiation damage modeling that can be combined with advanced inspection technologies to provide development of damage precursors and new nondestructive inspection methods for nuclear systems.
PNNL has a national leadership position in materials informatics, having formed a national steering committee with representation from academia, industry, data resources, and funding agencies to further enable techniques for the discovery of next-generation radiation detection materials through materials information processing, analysis, and optimization.
Using a combination of mechanical testing, microstructural analysis, and computer simulation, PNNL is studying a host of issues related to structural materials in the nuclear industry. A key issue being studied in fission reactors is the stress corrosion cracking mechanisms for stainless steels and nickel-based alloys, as well as hardening, segregation, swelling and brittleness of materials in the reactor core.
Nuclear Science Modeling
In collaboration with the University of Washington in Seattle, PNNL is conducting basic nuclear physics research, particularly in the area of weak interaction physics. The University of Washington's Nuclear Theory Center is one of the world's most highly regarded centers for nuclear theory including derivation of nuclear matrix elements and other nuclear structure modeling efforts.