Title: A computational approach to calculate the heat of transport of aqueous solutions,
Abstract: Thermal gradients induce concentration gradients in alkali halide solutions,
and the salt migrates towards hot or cold regions depending on the average
temperature of the solution. This effect has been interpreted using the heat of
transport, which provides a route to rationalize thermophoretic phenomena.
Early theories provide estimates of the heat of transport at infinite dilution.
These values are used to interpret thermodiffusion (Soret) and thermoelectric
(Seebeck) effects. However, accessing heats of transport of individual ions at
finite concentration remains an outstanding question both theoretically and
experimentally. Here we discuss a computational approach to calculate heats of
transport of aqueous solutions at finite concentrations, and apply our method
to study lithium chloride solutions at concentrations $>0.5$~M. The heats of
transport are significantly different for Li$^+$ and Cl$^-$ ions, unlike what
is expected at infinite dilution. We find theoretical evidence for the
existence of minima in the Soret coefficient of LiCl, where the magnitude of
the heat of transport is maximized. The Seebeck coefficient obtained from the
ionic heats of transport varies significantly with temperature and
concentration. We identify thermodynamic conditions leading to a maximization
of the thermoelectric response of aqueous solutions.