Official Resources
- Source Repository: https://github.com/gollumcode/gollum2
- Documentation: Included in repository
- License: Open source
Overview
Gollum is a next-generation quantum transport simulation tool for computing transport properties of nanoscale devices using the non-equilibrium Green's function (NEGF) method. It works with tight-binding Hamiltonians and can compute conductance, current-voltage characteristics, and thermoelectric properties.
Scientific domain: Quantum transport, NEGF, molecular electronics
Target user community: Researchers simulating quantum transport in molecular junctions and nanoscale devices
Theoretical Methods
- Non-equilibrium Green's function (NEGF) method
- Landauer-Büttiker formalism
- Tight-binding Hamiltonians
- Density functional theory (DFT) input
- Self-energy calculation
- Transmission function calculation
Capabilities (CRITICAL)
- Quantum conductance calculation
- Current-voltage (I-V) characteristics
- Transmission function
- Thermoelectric coefficients
- Tight-binding model transport
- DFT Hamiltonian input
- Multi-terminal transport
- Spin-dependent transport
Sources: GitHub repository, J. Chem. Phys.
Key Strengths
NEGF Transport:
- Full Green's function calculation
- Self-energy for leads
- Bias-dependent transport
- Multi-terminal support
Versatile Hamiltonian:
- Tight-binding models
- DFT-derived Hamiltonians
- Custom Hamiltonians
- Parameter exploration
Thermoelectric:
- Seebeck coefficient
- Peltier coefficient
- Thermal conductance
- ZT figure of merit
Inputs & Outputs
-
Input formats:
- Hamiltonian matrix files
- Lead self-energy parameters
- Transport configuration
-
Output data types:
- Transmission vs energy
- I-V characteristics
- Thermoelectric coefficients
- Local density of states
Interfaces & Ecosystem
- DFT codes: Hamiltonian extraction
- Python: Scripting
- NumPy: Numerical computation
Performance Characteristics
- Speed: Fast for TB models
- Accuracy: Depends on Hamiltonian quality
- System size: Thousands of orbitals
- Memory: Moderate
Computational Cost
- Transmission: Seconds to minutes
- I-V curve: Minutes
- Typical: Efficient
Limitations & Known Constraints
- Tight-binding: Quality depends on Hamiltonian
- No self-consistent NEGF: No Poisson-NEGF
- Limited documentation: Research code
- Small community: Research group code
Comparison with Other Codes
- vs Transiesta: Gollum is TB/NEGF, Transiesta is DFT+NEGF
- vs Kwant: Gollum focuses on molecular junctions, Kwant is general TB
- vs Nanodcal: Gollum is open source, Nanodcal is commercial
- Unique strength: Next-generation quantum transport for molecular junctions, thermoelectric properties
Application Areas
Molecular Electronics:
- Molecular junction conductance
- Single-molecule transport
- Break junction simulations
- Switching behavior
Thermoelectrics:
- Molecular thermoelectrics
- Seebeck coefficient prediction
- ZT optimization
- Energy harvesting
Nanoscale Devices:
- Quantum dot transport
- Nanowire conductance
- 2D material junctions
- Spin-dependent transport
Best Practices
Hamiltonian Quality:
- Use well-converged DFT Hamiltonians
- Test convergence with basis size
- Validate against known systems
- Consider spin-orbit coupling
Transport Calculation:
- Use sufficient energy grid
- Include sufficient lead layers
- Check convergence of self-energies
- Compare with Landauer limit
Community and Support
- Open source on GitHub
- Research code
- Limited documentation
- Related publications available
Verification & Sources
Primary sources:
- GitHub: https://github.com/gollumcode/gollum2
- Related publications from Lancaster University
Confidence: VERIFIED
Verification status: ✅ VERIFIED
- Source code: ACCESSIBLE (GitHub)
- Documentation: Included in repository
- Active development: Research code
- Specialized strength: Quantum transport for molecular junctions, NEGF, thermoelectric properties