PyCDFT

PyCDFT performs constrained density functional theory (CDFT) calculations to compute diabatic states and electronic couplings by adding constraint potentials to the Kohn–Sham Hamiltonian.

Key Features:

• Object-oriented framework: Provides an object-oriented and customizable Python framework for implementing CDFT workflows.
• Constrained DFT (CDFT): Generates diabatic states using density-based constraints applied during electronic structure calculations.
• Self-consistent-field (SCF) calculations: Supports single-point SCF calculations with applied constraints.
• Geometry optimizations: Performs constrained geometry optimizations of electronic states.
• Constraint incorporation: Incorporates constraint potentials directly into the Kohn–Sham Hamiltonian of underlying DFT codes.
• First-principles MD interfacing: Interfaces with first-principles molecular dynamics codes, explicitly demonstrated with Qbox.
• Parallel scalability: Designed for use in large-scale parallel computations with external DFT/MD codes.
• Benchmark validation: Validated by benchmarking electronic couplings between diabatic states across various organic molecules, producing results consistent with established CDFT implementations.

Scientific Applications:

• Diabatic state generation: Construction and analysis of diabatic states for charge-transfer and nonadiabatic studies.
• Electronic coupling calculation: Computation of electronic couplings between diabatic states in organic molecules.
• Constrained geometry studies: Exploration of potential energy surfaces and optimized geometries under electronic constraints.
• First-principles molecular dynamics: Integration with MD codes such as Qbox to study dynamical behavior of constrained electronic states.
• Quantum mechanical characterization: Investigation of quantum mechanical properties of molecular systems using CDFT.

Methodology:

PyCDFT adds constraint potentials to the Kohn–Sham Hamiltonian and performs self-consistent-field calculations and constrained geometry optimizations, interfaces with external DFT and first-principles MD codes (e.g., Qbox), and has been benchmarked via electronic coupling calculations between diabatic states in organic molecules.