Multimer embedding for molecular crystals utilizing up to tetramer interactions | JoVE Visualize

Area of Science:

Computational chemistry
Solid-state physics
Materials science

Background:

Molecular crystals exhibit complex crystallographic structures, often leading to multiple observed crystal forms.
Accurate computational modeling of these systems typically requires computationally intensive periodic density functional theory (DFT) with hybrid functionals.
Multimer embedding methods offer a computationally feasible alternative by combining lower-level periodic calculations with high-level corrections.

Purpose of the Study:

To extend multimer embedding methods by increasing the multimer order for lattice energies, atomic forces, stress tensor, and harmonic phonons.
To evaluate the impact of higher-order multimer interactions (up to tetramer for lattice energy, trimer for other properties) on computational accuracy.
To validate the enhanced method by comparing results to explicit high-level periodic DFT calculations using the X23 benchmark set.

Main Methods:

Utilizing an extended multimer embedding approach, incorporating up to tetramer interactions for lattice energies and trimer interactions for forces, stress tensor, and phonons.
Performing calculations with PBE0+MBD multimers embedded within periodic PBE+MBD calculations.
Comparing the results against explicit periodic PBE0+MBD calculations on the X23 molecular crystal benchmark set.

Main Results:

Tetramer interactions significantly improve the accuracy of lattice energy approximations.
Trimer interactions are essential for accurately describing the stress tensor, achieving cell volume predictions within 0.3% of high-level calculations.
Inclusion of trimer interactions enhances the prediction of vibrational properties, with Gamma-point frequencies and vibrational free energies closely matching high-level results.

Conclusions:

The extended multimer embedding approach provides a computationally efficient and accurate method for modeling molecular crystals.
Higher-order multimer interactions, particularly up to the trimer level, are crucial for capturing key solid-state properties.
This method offers a viable alternative to expensive full periodic calculations for complex molecular crystal systems.