Bottom-up coarse-grained simulations of electric-field-induced biaxiality and switching dynamics in liquid crystals of board-like molecules.

Electric fields can alter the orientational symmetry of liquid crystals, driving the emergence of biaxial order with potential relevance for next-generation electro-optical devices. Here, we present a coarse-grained (CG) model for a liquid crystal of board-like mesogens that enables a direct connection with our previous atomistic molecular dynamics simulations. The model is constructed through a particle-based mapping scheme that preserves the intrinsic anisotropy of the molecular core while enabling access to larger system sizes and longer time scales. Effective bonded and non-bonded interactions are obtained within a bottom-up force-matching framework and validated against atomistic reference data through structural and orientational correlations. A comparison with the atomistic reference allows us to assess both the capabilities and the limitations of the present CG representation, particularly in relation to the subtle balance between nematic and weak smectic-A organisation. Building on this framework, we then investigate the response of the system to externally applied electric fields. The model successfully captures field-induced reorientation dynamics and reveals a strong dependence of the ordering kinetics on field strength. Stronger fields substantially accelerate the evolution towards equilibrium, eventually leading to a rapid-alignment regime at high field strengths. After the field is removed, the system retains residual orientational memory rather than fully relaxing to its initial disordered state, suggesting persistent field-induced correlations that may affect subsequent switching processes. Most importantly, the external field promotes the formation of a biaxial nematic phase, highlighting the ability of the model to capture subtle symmetry-breaking phenomena induced under non-equilibrium conditions and relevant to electro-optical applications. The present CG model provides an efficient and physically consistent framework for exploring equilibrium structures, switching dynamics, and field-driven non-ordering in liquid-crystalline materials.