Intermolecular Interactions: From Dimers to Crystals

Welcome to the AWSCC 2025 Workshop! In this workshop we'll explore some of the background on intermolecular (or non-bonded) interactions, predicting the energies associated with these interactions, and how they might be used to rationalise/understand crystal structures and crystal growth.

This comprehensive material is designed to serve as both a workshop guide and a reference for independent study. While we may not cover everything during the workshop, all resources will remain available for further exploration.

Feel free to interrupt and ask questions!

If you've got a question, odds are someone else is having a similar issue or query!

Hopeful Timeline:

• 0:00-0:10 - Setup & Introduction
• 0:10-0:50 - Pair Energies
• 0:50-1:10 - Clusters & Crystals
• 1:10-1:30 - Crystal Growth

Workshop Materials

📄️ 0. Setup (10 minutes)

Welcome to the AWSCC 2025 Workshop on Intermolecular Interactions! This setup guide will get you ready for the hands-on exercises.

📄️ 1. Intermolecular Interactions: From Theory to Practice

Much of chemistry and materials science involves condensed matter, that is to intermolecular interactions (or perhaps more accurately non-bonded interactions). Understanding these interactions is therefore fundamental to many applications of computational chemistry. Since theoretical and computational chemistry is generally focused on getting the best answer in a tractable amount of computer time, it's essential to know which kinds of interactions are important for which systems, and cheap and dirty can we be in their approximation when explaining or predicting some observable phenomenon.

📄️ 2. From Pairs to Crystals: Many-Body Effects

Moving from isolated pairs to clusters and crystals reveals fundamental challenges in computational chemistry. The total energy is not simply the sum of pairwise interactions. This section explores how to calculate lattice energies using the occ elat command and estimate energies with fast semi-empirical methods like xTB.

📄️ 3. Crystal Growth: Putting It All Together

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📄️ Appendix: CE-1p

The CE-1p (CrystalExplorer 1-parameter) model provides fast estimation of molecular dimer interaction energies, building upon previous CE models to address their limitations.

📄️ Appendix: Crystal Growth Theory and Computational Protocol

Crystal growth is one of those areas where theory meets practice in fascinating (and often frustrating) ways. You can have the most beautiful theoretical understanding of molecular interactions, but when it comes to predicting what shape crystals will actually grow into, you quickly realize that the devil is in the details - and there are a lot of details.

Resources

• Workshop Repository
• OCC (Open Computational Chemistry) Documentation
• CE-1p model info
• Crystal growth background

After the Workshop

Continue exploring:

1. Apply methods to your own molecules
2. Try advanced exercises in the repository
3. Come and have a chat!