Smeagol

Official Resources

• Homepage: https://www.tcd.ie/Physics/Smeagol/
• Documentation: https://www.tcd.ie/Physics/Smeagol/manuals.html
• Source Repository: Distributed via website (Academic license)
• License: Academic License (Free)

Overview

Smeagol is a software package for calculating spin-dependent electron transport in nanoscale devices. It interfaces with the SIESTA DFT code to perform Non-Equilibrium Green's Function (NEGF) calculations. Smeagol is specifically designed for spintronics, handling magnetic materials, spin torque, and non-collinear magnetism in transport junctions.

Scientific domain: Quantum transport, spintronics, NEGF-DFT
Target user community: Spintronics researchers, magnetics community

Theoretical Methods

• Non-Equilibrium Green's Function (NEGF)
• Density Functional Theory (via SIESTA)
• Spin-dependent transport
• Non-collinear magnetism
• Spin-Transfer Torque (STT)
• Inelastic scattering (weak electron-phonon coupling)

Capabilities (CRITICAL)

• Transport: I-V characteristics, transmission coefficients, magnetoresistance
• Spin: Spin-polarized currents, giant magnetoresistance (GMR), tunneling magnetoresistance (TMR)
• Torque: Calculation of spin-transfer torque vectors
• Magnetic: Self-consistent calculation of magnetic moments under bias
• Interfaces: Metal-molecule-metal junctions, magnetic tunnel junctions

Sources: Smeagol website, Phys. Rev. B 73, 085414 (2006)

Inputs & Outputs

• Input formats: SIESTA fdf files, electrode Hamiltonians
• Output data types: Current-voltage curves, transmission spectra, density matrices

Interfaces & Ecosystem

• SIESTA: Requires SIESTA as the DFT engine
• Plotting: Standard text output for plotting

Workflow and Usage

1. Calculate bulk electrodes using SIESTA.
2. Setup transport geometry (leads + scattering region).
3. Run Smeagol (modified SIESTA executable) to solve NEGF self-consistently.
4. Extract transmission and currents.

Performance Characteristics

• Computationally intensive (NEGF inversion)
• Parallelized (MPI)
• Memory scaling depends on system cross-section

Application Areas

• Molecular spintronics
• Magnetic Tunnel Junctions (MTJ)
• Spin filters
• Graphene spintronics

Community and Support

• Developed by Sanvito Group (Trinity College Dublin)
• Academic user base
• Regular workshops (Computational Spintronics)

Verification & Sources

Primary sources:

1. Homepage: https://www.tcd.ie/Physics/Smeagol/
2. Publication: A. R. Rocha et al., Phys. Rev. B 73, 085414 (2006)

Confidence: VERIFIED

Verification status: ✅ VERIFIED

• Website: ACTIVE
• Documentation: AVAILABLE
• Source: ACADEMIC (Registration)
• Development: ACTIVE (Sanvito Group)
• Applications: Spintronics, NEGF, magnetic transport