Thermal Conductivities of Molecular Liquids by Reverse Nonequilibrium Molecular Dynamics

Abstract

The reverse nonequilibrium molecular dynamics method for thermal conductivities is adapted to the investigation of molecular fluids. The method generates a heat flux through the system by suitably exchanging velocities of particles located in different regions. From the resulting temperature gradient, the thermal conductivity is then calculated. Different variants of the algorithm and their combinations with other system parameters are tested: exchange of atomic velocities versus exchange of molecular center-of-mass velocities, different exchange frequencies, molecular models with bond constraints versus models with flexible bonds, united-atom versus all-atom models, and presence versus absence of a thermostat. To help establish the range of applicability, the algorithm is tested on different models of benzene, cyclohexane, water, and n-hexane. We find that the algorithm is robust and that the calculated thermal conductivities are insensitive to variations in its control parameters. The force field, in contrast, has a major influence on the value of the thermal conductivity. While calculated and experimental thermal conductivities fall into the same order of magnitude, in most cases the calculated values are systematically larger. United-atom force fields seem to do better than all-atom force fields, possibly because they remove high-frequency degrees of freedom from the simulation, which, in nature, are quantum-mechanical oscillators in their ground state and do not contribute to heat conduction.

Nonequilibrium molecular dynamics simulations of the thermal conductivity of water: A systematic investigation of the SPC/E and TIP4P/2005 models

“…At lower densities we find again larger discrepancies that might be connected to the inaccuracy of the models in reproducing the properties of water in the low density regime. It is encouraging that all the water models investigated to date reproduce Diamonds represent simulation data from reference 17 and triangles from reference 19 .…”

“…The thermal conductivity of water has been computed before using a variety of techniques and models [17][18][19][20][21][22] . Most of these studies have focused on a specific temperature and density or a narrow range of thermodynamic states.…”

Correlation between thermal conductivity and bond length alternation in carbon nanotubes: A combined reverse nonequilibrium molecular dynamics—Crystal orbital analysis

“…67 In analogy to the broad application of the INDO CO Hamiltonian, the RNEMD approach has been also used to study the transport quantities of many materials. [68][69][70][71][72] Originally this approach had been developed for atomic liquids. Later it had been extended to molecular fluids as well as to crystalline and amorphous polymers.…”

Multiscale Modeling of Multiphase Fluid Flow

“…The thermal conductivities of aqueous SDS solutions at a range of surfactant concentrations were computed by Müller-Plathe's method [95,96] from NEMD simulations. The values of the thermal conductivity of aqueous SDS solutions, computed with flexible and rigid TIP3P water model at room and boiling temperature and different surfactant concentrations are listed in Table 3-2.…”

“…We computed the thermal conductivity by carrying out NEMD simulations where heat flux is introduced in the system which leads to establishing a temperature gradient across the system as proposed by Müller-Plathe [95]. We used the Müller-Plathe method of imposing heat flux [96] which involves swapping the kinetic energy of the hottest particle in a predefined cold region of the system with the kinetic energy of the coldest particle in the predefined hot region of the system thus conserving the total energy of the system while inducing heat flux from the hot region (heat source) to the cold region (heat sink). In response to the heat flux through the system, a temperature gradient is established.…”