# Inverse design of charged colloidal particle interactions for self assembly into specified crystal structures

## TL;DR

This paper develops an inverse design method to tune charged colloidal interactions, enabling self-assembly into specific crystal structures like bcc, using advanced optimization algorithms and phase boundary sensing.

## Contribution

It introduces a statistical physics-inspired inverse design approach combined with CMA-ES to target and stabilize specific colloidal crystal structures.

## Key findings

- Successfully targeted bcc structure in simulations
- The optimization algorithms accurately detect phase boundaries
- CMA-ES outperforms the initial method in efficiency

## Abstract

We study the inverse problem of tuning interaction parameters between charged colloidal particles interacting with a hard-core repulsive Yukawa potential, so that they assemble into specified crystal structures. Here, we target the body-centered-cubic (bcc) structure which is only stable in a small region in the phase diagram of charged colloids and is, therefore, challenging to find. In order to achieve this goal, we use the statistical fluctuations in the bond orientational order parameters to tune the interaction parameters for the bcc structure, while initializing the system in the fluid phase, using the Statistical Physics-inspired Inverse Design (SP-ID) algorithm [1]. We also find that this optimization algorithm correctly senses the fluid-solid phase boundaries for charged colloids. Finally, we repeat the procedure employing the Covariance Matrix Adaptation - Evolution Strategy (CMA-ES), a cutting edge optimization technique, and compare the relative efficacy of the two methods.