# Resolution limit of data-driven coarse-grained models spanning chemical space

## TL;DR

This paper investigates the resolution limits of data-driven coarse-grained models in chemical space, proposing new design criteria, evaluating models with varying bead types, and highlighting the trade-offs between transferability and specificity.

## Contribution

It introduces criteria for designing chemically transferable coarse-grained models and evaluates the impact of bead type number on model accuracy and chemical mapping resolution.

## Key findings

- Fewer bead types can achieve performance comparable to more complex models.
- Increasing bead types reduces uncertainty in chemical back-mapping.
- A resolution limit exists when using water/octanol partition energy as the sole descriptor.

## Abstract

Increasing the efficiency of materials design and discovery remains a significant challenge, especially given the prohibitively large size of chemical compound space. The use of a chemically transferable coarse-grained model enables different molecular fragments to map to the same bead type, while also reducing computational expense. These properties further increase screening efficiency, as many compounds are screened through the use of a single coarse-grained simulation, effectively reducing the size of chemical compound space. Here, we propose new criteria for the rational design of coarse-grained models that allows for the optimization of their chemical transferability and evaluate the Martini model within this framework. We further investigate the scope of this chemical transferability by parameterizing three Martini-like models, in which the number of bead types ranges from five to sixteen for the different force fields. We then implement a Bayesian approach to determining which chemical groups are more likely to be present on fragments corresponding to specific bead types for each model. We demonstrate that a level of performance and accuracy comparable to Martini can be obtained by using a force field with fewer bead types. However, the advantage of including more bead types is a reduction of uncertainty with respect to back-mapping these bead types to specific chemistries. Just as reducing the size of the coarse-grained particles leads to a finer mapping of conformational space, increasing the number of bead types yields a finer mapping of chemical compound space. Finally, we note that, due to the relatively large size of the chemical fragments that map to a single martini bead, a clear resolution limit arises when using the water/octanol partition free energy as the only descriptor when coarse-graining chemical compound space.