New Simulation Framework Bridges Atomic and Large-Scale Physics in Fusion Research
Extreme Conditions Inside Inertial Confinement Fusion
In inertial confinement fusion, a tiny fuel capsule starts out at near-zero temperatures and under almost vacuum-like pressure.
When powerful lasers compress the fuel to initiate fusion, it is rapidly heated to millions of degrees and squeezed to pressures comparable to those at the Sun's core — all within an extraordinarily small space and an instant of time.
To make sense of this extreme transformation, scientists must understand large-scale conditions such as temperature and pressure across the entire target chamber. At the same time, they require detailed insight into the behaviour of the material and its individual atoms.
Until recently, computer simulations have struggled to connect these vastly different scales and conditions within a single model.
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New Simulations Framework Bridges the Gap
In research published in Physical Review E, scientists from Lawrence Livermore National Laboratory (LLNL) and the University of California, Davis have introduced a new simulation framework that link atom-scale modelling directly with code describing the macroscopic world — all within a single, unified system.
"We are dealing with atoms measured in nanometers on one side and large-scale flow fields stretching over meters on the other," explains Tim Linke, a PhD researchers at UC Davis working in residence at LLNL. "The material itself is what connects these two extremes."
To establish this link, the team merged a hydrodynamics code developed at LLNL with a molecular dynamics code from Sandia National Laboratories.
How the Unified Model Works
The hydrodynamics model captures large-scale conditions and their evolution at specific points in space
This information is passed directly to the molecular dynamics code
The molecular dynamics model determines how individual atoms respond
Both simulations run simultaneously, allowing real-time atom-level calculations alongside the large-scale model
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Computational Challenges and Broader Applications
Running this framework demands enormous computational power. After hitting severe limitations on other platforms, the research team redesigned their code specifically for the accelerated processing unit architecture of LLNL's Tuolumne supercomputer, which mirrors the design of tis exascale counterpart, EI Capitan.
The approach opens the door to a wide range of applications spanning:
- Fusion research
- Planetary science
- Astrophysical events such as asteroid impacts
Broader Scientific Applications
"This paper is deliberately broad," says Linke. "We wanted to keep it that way because the method can be applied to phase transitions, material defects, chemical reactions and many other problems where microscopic detail must be connected to behaviour on a macroscopic scale."
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Potential for Future Research and Insights
The newly developed approach is especially valuable for systems that change their chemical composition as a simulations progresses.
"This is precisely what happens in wetted foam targets used at the National Ignition Facility," explains LLNL scientist and co-author Sébastien Hamel. "These targets begin as a microscopically mixed combination of foam and deuterium. As compression and heating occur, chemical bonds break and the system becomes increasingly atomically mixed and more uniform."
Advancing Extreme-Matter Understanding
The simulation code offers a new way to better understand the material properties under such extreme conditions.
"This work opens the door to applications where non-equilibrium material behaviour — including phase transitions, such as liquid to solid and chemical reactions — can be simulated alongside hydrodynamics using atomistic insight. That represents the next stage of our research," adds LLNL scientist and co-author Dane Sterbentz.
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