Galilean-invariant Nosé-Hoover-type thermostats

Abstract

A new pairwise Nose-Hoover type thermostat for molecular dynamics (MD) simulations which is similar in construction to the pair-velocity thermostat of Allen and Schmid, [Mol. Simul. 33, 21 (2007)] (AS) but is based on the configurational thermostat is proposed and tested. Both thermostats generate the canonical velocity distribution, are Galilean invariant, and conserve linear and angular momentum. The unique feature of the pairwise thermostats is an unconditional conservation of the total angular momentum, which is important for thermalizing isolated systems and those nonequilibrium bulk systems manifesting local rotating currents. These thermostats were benchmarked against the corresponding Nose-Hoover (NH) and Braga-Travis prescriptions, being based on the kinetic and configurational definitions of temperature, respectively. Some differences between the shear-rate-dependent shear viscosity from Sllod nonequilibrium MD are observed at high shear rates using the different thermostats. The thermostats based on the configurational temperature produced very similar monotically decaying shear viscosity (shear thinning) with increasing shear rate, while the NH method showed discontinuous shear thinning into a string phase, and the AS method produced a continuous increase of viscosity (shear thickening), after a shear thinning region at lower shear rates. Both pairwise additive thermostats are neither purely kinetic nor configurational in definition, and possible directions for further improvement in certain aspects are discussed.

Central-force decomposition of spline-based modified embedded atom method potential

“…The expressions for both of the above-mentioned derivatives are also of use in recentlyproposed thermostats based on the concept of configurational temperature [94][95][96]. The results presented here can thus also be viewed as facilitating future studies of non-equilibrium properties, for which such thermostats are invaluable.…”

A Nosé-Hoover Thermostat Adapted to a Slab Geometry

“…2 shows that the calculated temperature of the walls responds relatively quickly to the new target value. There are small oscillations in the instantaneous temperature trace just after the temperature step, which is a well known feature of the NH thermostat [15]. Significantly, the temperature of the confined part of the system eventually achieves the target temperature.…”

“…We note that the NHASv thermostat can be considered to be a special case of the generalised Nosé-Hoover equations discussed by Kusnezov et al [16]. More details on the NHASv thermostat and its configurational temperature counterpart are given in our publication [15].…”

“…Another type of Nosé-Hoover thermostat is the Galileaninvariant thermostat, which acts on pairs of particles rather than single particles [14,15]. A deterministic, Galileaninvariant thermostat based on relative velocities was derived by Allen and Schmid [14], which we refer to as 'NHASv'.…”