Multimer Embedding Approach for Molecular Crystals up to Harmonic Vibrational Properties

Area of Science:

• Computational chemistry
• Materials science
• Solid-state physics

Background:

• Accurate molecular crystal calculations are vital for drug design and crystal engineering.
• High-level periodic density functional calculations (e.g., hybrid functionals) are computationally expensive for these systems.
• Embedding methods offer a way to circumvent high computational costs by combining low-cost and high-level calculations.

Purpose of the Study:

• To extend multimer embedding methods for energy corrections including trimer interactions.
• To enable the calculation of harmonic vibrational properties up to the dimer level.
• To evaluate the accuracy of this extended embedding approach for molecular crystals.

Main Methods:

• Developed and applied a multimer embedding approach incorporating trimer interactions and dimer vibrational properties.
• Used the X23 benchmark set of molecular crystals for evaluation.
• Approximated periodic hybrid density functional (PBE0+MBD) calculations using less expensive generalized-gradient approximation (PBE+MBD) calculations with embedding.

Main Results:

• Trimer interactions are essential for approximating lattice energies within 1 kJ/mol.
• Trimer interactions may improve lattice constants and cell volumes.
• Vibrational properties are accurately captured at monomer and dimer levels, allowing vibrational free energy approximation within 1 kJ/mol at room temperature.

Conclusions:

• The extended multimer embedding approach provides accurate lattice energies and vibrational properties for molecular crystals.
• This method offers a computationally efficient alternative to expensive periodic calculations for drug design and crystal engineering.
• Inclusion of trimer interactions is key for high accuracy in lattice energy calculations.