FYI:

Particle models are, in principle, offshoots of molecular dynamics (MD) adapted to simulation of materials at coarser scales. The role of atom is taken over by a continuum particle or quasi-particle, a basic constitutive unit that can represent, for example, a grain of ceramics, a concrete aggregate, and a particle of a composite. The computation domain is discretised into regular or random network of such particles generally interacting through nonlinear potentials within the realm of Newtonian dynamics. The model parameters should be identifiable with the macroscopic elastic, inelastic, and fracture properties of the material they aspire to represent, and the model should be structured in accordance with its morphology.

Cited from 2015 Handbook of Damage Mechanics;Nano to Macro Scale for Materials and Structures

Particle model is a model to consider similar behaving things as a single entity. In some cases, 'nucleus and electron' are considered as a single entity as a soft or hard ball/sphere to make calculation simpler.

Molecular dynamics is a technique where particle model can be used to simplify the problem neglecting the electronic states and their interaction.

MD can be considered as a special case of a particle model, in which particles are atoms and the force field is inspired by genuine (sort of) interatomic forces. In a more general case, a particle may represent any given component of a system and the force field may involve unphysical terms so that the system would demonstrate a desired macroscopic behavior.