Official Resources
- Homepage: https://github.com/LLNL/USER-EPH
- Source Repository: https://github.com/LLNL/USER-EPH
- License: MIT License
Overview
USER-EPH is a LAMMPS extension package for incorporating electron-phonon coupling effects in molecular dynamics simulations. Developed at Lawrence Livermore National Laboratory, it enables simulation of energy exchange between electronic and ionic subsystems.
Scientific domain: Electron-phonon coupling, two-temperature model, radiation damage
Target user community: LAMMPS users studying electron-phonon energy transfer
Theoretical Methods
- Two-temperature model (TTM)
- Electronic heat diffusion
- Electron-phonon coupling parameter
- Langevin thermostat for electrons
- Energy exchange dynamics
- Non-equilibrium electron-ion dynamics
Capabilities (CRITICAL)
- Electron-phonon energy transfer
- Two-temperature MD simulations
- Electronic heat diffusion
- Radiation damage simulations
- Laser-matter interactions
- Non-equilibrium dynamics
- LAMMPS integration
Key Strengths
LAMMPS Integration:
- Standard LAMMPS package
- Easy installation
- Familiar interface
- Large user base
TTM Implementation:
- Robust two-temperature model
- Electronic subsystem
- Energy coupling
- Non-equilibrium physics
Inputs & Outputs
-
Input formats:
- LAMMPS input scripts
- Electronic parameters
- Coupling coefficients
-
Output data types:
- Electronic temperature
- Ionic temperature
- Energy transfer rates
- Standard LAMMPS output
Interfaces & Ecosystem
- LAMMPS: Primary MD code
- fix eph: Main LAMMPS fix
- Compatible with LAMMPS potentials
Advanced Features
- Two-temperature model: Electronic and ionic subsystems
- Electronic heat diffusion: Spatial temperature evolution
- Langevin thermostat: Stochastic electron-ion coupling
- Energy exchange: Non-equilibrium dynamics
- LAMMPS fix: Standard LAMMPS integration
- Parallel support: MPI-compatible
Performance Characteristics
- LAMMPS-based: Efficient MD
- Scales with system size
- MPI parallelization available
Computational Cost
- Standard LAMMPS MD cost
- Additional overhead for TTM: Moderate
- Electronic grid: Scales with spatial resolution
- Overall: Comparable to standard LAMMPS simulations
Best Practices
- Validate electron-phonon coupling parameter
- Check electronic temperature evolution
- Use appropriate time steps for energy transfer
- Compare with experimental relaxation times
Limitations & Known Constraints
- Requires coupling parameter input
- Simplified electronic model
- Classical ion dynamics
- Parameter fitting needed
Application Areas
- Radiation damage
- Laser ablation
- Ion irradiation
- Ultrafast dynamics
- Materials under extreme conditions
Verification & Sources
Primary sources:
- GitHub: https://github.com/LLNL/USER-EPH
- A. Tamm et al., Phys. Rev. B 94, 024305 (2016)
Confidence: VERIFIED
Verification status: ✅ VERIFIED
- Source code: OPEN (GitHub, MIT)
- LLNL development