Official Resources
- Homepage: https://github.com/lucydot/effmass
- Documentation: https://effmass.readthedocs.io/
- Source Repository: https://github.com/lucydot/effmass
- License: MIT License
Overview
effmass is a Python package for calculating the effective mass of charge carriers (electrons and holes) from electronic band structures. It supports both parabolic and non-parabolic definitions of effective mass and provides tools for selecting band segments extrema. effmass is designed to work with outputs from major DFT codes like VASP, FHI-aims, CASTEP, and Quantum ESPRESSO.
Scientific domain: Semiconductor physics, transport properties, electronic structure
Target user community: Materials scientists, device physicists, PV researchers
Theoretical Methods
- Parabolic effective mass (curvature at band extrema)
- Non-parabolic kane dispersion fitting
- Finite difference method (3-point, 5-point)
- Least-squares fitting
- Density-of-states (DOS) effective mass
- Conductivity effective mass
- Optical effective mass
Capabilities (CRITICAL)
- Automatic identification of CBM and VBM
- Calculation of effective mass tensors
- Support for multiple definitions of effective mass (transport, optical, curvature)
- Handling of multiple bands and degeneracy
- Integration with ASE and vasppy
- Command-line interface and Python API
- Visualization of band segments and fits
Sources: effmass documentation, J. Open Source Softw. 3, 797 (2018)
Inputs & Outputs
- Input formats: VASP (vasprun.xml, OUTCAR/PROCAR), CASTEP, FHI-aims, QE, cube files
- Output data types: Effective mass values (tensor/scalar), plots of fits, JSON summary
Interfaces & Ecosystem
- VASP: Primary target via
vasprun.xml
- ASE: Compatible with ASE Atoms objects
- Cli:
effmass command line tool
- Python: Library for custom analysis
Workflow and Usage
- Perform DFT band structure calculation (dense k-mesh near extrema).
- Run effmass:
effmass-cli (interactive) or script.
- Select extrema and directions.
- Choose effective mass definition (e.g., curvature).
- Output effective masses and plots.
Performance Characteristics
- Very fast post-processing
- Depends on file I/O speed for large vasprun.xml
Application Areas
- Photovoltaics (carrier mobility)
- Thermoelectrics
- Transparent conducting oxides
- Semiconductor device modeling
Community and Support
- Open-source (MIT)
- GitHub repository
- Developed by Lucy Whalley (Imperial College London / Northumbria University)
Verification & Sources
Primary sources:
- Homepage: https://github.com/lucydot/effmass
- Documentation: https://effmass.readthedocs.io/
- Publication: L. D. Whalley, J. Open Source Softw. 3, 797 (2018)
Confidence: VERIFIED
Verification status: ✅ VERIFIED
- Website: ACTIVE
- Documentation: AVAILABLE
- Source: OPEN (GitHub)
- Development: ACTIVE (Whalley)
- Applications: Effective mass, carrier transport, band fitting