# Molecular Simulation/Transport properties

## Viscosity

editThe viscosity of a liquid is defined by the drag force experienced by a moving plate separated from a stationary plate by a layer of the liquid.

u is the speed of the moving plate. h is distance by which the two plates are separated. A is the surface area of the moving plate.

can be calculated from a molecular dynamics simulation using the Green–Kubo relation,

P_{xy} is the xy component of the pressure tensor. The xz or yx off-diagonal components can be used instead.

## Thermal Conductivity

editThe thermal conductivity of a liquid is defined by the rate of heat transfer between an upper and lower plate at different temperatures (T_{1} and T_{2}).

The Green-Kubo relation for thermal conductivity relates lambda to the autocorrelation function of the heat current,