This directory contains the interface between ABACUS and Hefei-NAMD, an open-source, ab initio non-adiabatic molecular dynamics (NAMD) package designed for simulating ultrafast excited-state carrier dynamics in condensed-matter systems.

Hefei-NAMD is an open-source, ab initio non-adiabatic molecular dynamics (NAMD) package designed for simulating ultrafast excited-state carrier dynamics in condensed-matter systems (e.g., semiconductors, 2D materials, oxides, and interfaces) across real/momentum space, energy, and time domains. Developed primarily by Prof. Qijing Zheng (University of Science and Technology of China, USTC) and collaborators, it is hosted publicly on GitHub: github.com/QijingZheng/Hefei-NAMD.

• Theoretical foundation: Combines time-dependent density-functional theory (TDDFT) with the fewest-switches surface hopping (FSSH) algorithm and decoherence-induced surface hopping (DISH) to treat electron–phonon coupling and non-adiabatic transitions between electronic states.
• Key quantities: Computes non-adiabatic coupling (NAC) matrices and electron–phonon coupling (EPC) from first-principles wavefunctions.
• Implementation: Mainly written in Fortran (≈80%) with Python pre/post-processing tools; minimal external dependencies, easy to compile via make.

• Interfaces to major DFT codes: Works natively with VASP and ABACUS (via abacus-namd scripts) to read MD trajectories, wavefunctions, and band structures.
• Real- and momentum-space dynamics: Supports carrier relaxation, recombination, hot-carrier transport, and exciton dynamics.
• Advanced capabilities:
  • Spin–orbit coupling (SOC) (via NAMDwithSOC extension).
  • Light–matter interaction (NAMD-LMI) for photoexcitation and stimulated emission.
  • Finite-temperature MD and trajectory sampling.
• Parallelization: MPI support for high-throughput calculations.

1. Geometry optimization → ab initio MD → trajectory snapshots.
2. DFT single-points (SCF) → wavefunction output.
3. NAMD simulation → analysis of carrier lifetime, relaxation pathways, etc.

• Carrier relaxation/recombination: e.g., in TiO₂, perovskites, 2D van der Waals heterostructures.
• Hot-carrier dynamics and transport in photovoltaics and photocatalysts.
• Exciton dissociation and charge transfer at interfaces.
• Ultrafast spectroscopy (transient absorption, photoluminescence) interpretation.

• Open-source: Free under academic license; source code, manual, tutorials, and examples are fully public.
• Citation: Users are requested to cite core publications (e.g., Zheng et al., WIREs Comput. Mol. Sci., 2021).

In short, Hefei-NAMD is a widely used, community-driven tool for first-principles excited-state dynamics in materials science, valued for its efficiency, flexibility, and compatibility with standard DFT workflows.

The ABACUS-Hefei-NAMD interface allows ABACUS to generate the necessary files for Hefei-NAMD calculations, including overlap matrices, wavefunctions, and Hamiltonian matrices.

• cal_syns: Set to 1 to calculate asynchronous overlap matrix
• dmax: Maximum displacement of all atoms in one step (in bohr) for calculating asynchronous overlap matrix
• out_wfc_lcao: Set to 1 to output wavefunction files
• out_mat_hs: Set to 1 to output Hamiltonian and overlap matrix files

The example01 directory contains a simple example demonstrating how to set up an ABACUS calculation that generates the necessary files for Hefei-NAMD.

1. Set up an ABACUS calculation with the appropriate parameters for Hefei-NAMD (see examples)
2. Run ABACUS to generate the necessary output files
3. Use the generated files as input for Hefei-NAMD calculations