Thermophoretic force on nanoparticles in free molecule regime

Thermophoresis refers to the motion of small particles suspending in a fluid with non-uniform temperature distribution due gradient around particle. Usually, molecules coming from hot side carry more kinetic energy than those cold side, which results net thermophoretic force direction opposite gradient. Since it was discovered 100 years ago, thermophoresis has been major importance variety applications, where can play either beneficial role or adverse role, including material synthesis, micro- and nano-fabrication, environmental science. Therefore, is necessary accurately evaluate force. In present work, on nanoparticles examined free molecule regime by using non-equilibrium dynamics (MD) simulation. It widely accepted that conforms Waldmann equation for large Knudsen numbers. However, effect nonrigid-body interactions between particle gas molecules, might deviate greatly classical theory. our MD model, single nanoparticle diameter several nanometers suspends diluted gas. The Lennard-Jones (L-J) potential employed simulate intermolecular interactions. To avoid deforming nanoparticle, solid within are linked their nearest neighbors through finite extensible nonlinear elastic bonding potential. calculated imposing harmonic eliminates Brownian thermophoresis. effective thermal conductivity ambient volume effect. found theory still valid case weak gas-particle interaction high temperature. With increase strength decrease temperature, invalid collisions adsorption surface. By considering modified size, theoretical accord simulations quite well.