LICHEM

LICHEM performs QM/MM calculations by interfacing quantum chemistry and molecular mechanics codes to enable multipolar and polarizable force-field simulations for accurate modeling of molecular interactions.

Key Features:

• Code interfaces: Interfaces with Gaussian, PSI4, NWChem, TINKER, and TINKER-HP to combine QM and MM software capabilities.
• Multipolar and polarizable force fields: Supports multipolar and polarizable force fields within QM/MM simulations to capture explicit polarization effects.
• Force and energy extraction: Extracts forces and energies from unmodified QM and MM software packages for combined QM/MM analysis.
• Supported calculations: Performs geometry optimizations, single-point energy calculations, and Monte Carlo simulations.
• Covalent QM/MM boundaries: Treats covalent bonds across QM and MM regions using a pseudo-bond approach to ensure smooth QM/MM coupling.
• Validation systems: Has been tested on water clusters and small peptides to demonstrate capture of explicit polarization effects.

Scientific Applications:

• Modeling explicit polarization: Investigation of explicit polarization effects in molecular systems using multipolar and polarizable force fields.
• QM/MM studies with covalent boundaries: Simulations of systems where QM and MM regions are connected by covalent bonds using pseudo-bond treatment.
• Energetics and structure determination: Geometry optimizations and single-point energy evaluations of molecular systems combining QM and MM methods.
• Sampling and statistical studies: Monte Carlo simulations incorporating QM/MM-derived energies for statistical sampling of molecular conformations.

Methodology:

Interfaces with Gaussian, PSI4, NWChem, TINKER, and TINKER-HP; extracts forces and energies from unmodified QM and MM packages; employs multipolar/polarizable force fields in QM/MM; performs geometry optimizations, single-point energy calculations, and Monte Carlo simulations; uses a pseudo-bond approach for covalent QM/MM boundaries.