interparticle

Interparticle is an adjective used in physics and chemistry to describe phenomena arising from forces and interactions between particles within a system. In modeling such systems, the interaction is often represented by an interparticle potential U(r), a function of the separation distance r between two particles. The potential encodes attractions and repulsions that influence structure and dynamics, and it distinguishes interparticle effects from external potentials that act on individual particles.

Common forms of interparticle potentials include the Lennard-Jones potential for neutral atoms and molecules, the Coulomb potential for charged species, and Yukawa or screened-Coulomb potentials in plasmas and electrolytes. In colloids, DLVO theory combines van der Waals attraction with electrostatic repulsion. In solids, effective pair potentials arise from bonding and antibonding interactions, while in quantum systems exchange and correlation effects contribute to the effective interparticle interaction.

Interparticle interactions determine the arrangement of particles, phase behavior, and transport properties. They give rise to spatial correlations characterized by the pair distribution function g(r) and the structure factor S(k). Temperature, density, and external fields modulate these interactions, driving transitions between gas, liquid, and solid states.

Modeling interparticle forces is a central task in simulations and theory. Molecular dynamics and Monte Carlo methods compute trajectories or configurations from specified U(r). Quantum approaches account for exchange and correlation effects. Long-range interactions pose computational challenges and are often treated with techniques such as Ewald summation or fast multipole methods.

Interparticle concepts apply across disciplines: condensed matter physics, chemistry, soft matter, biophysics, and astrophysics, where gravitational interparticle forces act in the same framework at vastly different scales. They are distinguished from external potentials that act on individual particles regardless of others.