  Recent dynamic compression experiments [M. D. Knudson et al., Science 348,
1455 (2015); P. M. Celliers et al., Science 361, 677 (2018)] have observed the
insulator-metal transition in dense liquid deuterium, but with an approximately
95 GPa difference in the quoted pressures for the transition at comparable
estimated temperatures. It was claimed in the latter of these two papers that a
very large latent heat effect on the temperature was overlooked in the first,
requiring correction of those temperatures downward by a factor of two, thereby
putting both experiments on the same theoretical phase boundary and reconciling
the pressure discrepancy. We have performed extensive path-integral molecular
dynamics calculations with density functional theory to directly calculate the
isentropic temperature drop due to latent heat in the insulator-metal
transition for dense liquid deuterium and show that this large temperature drop
is not consistent with the underlying thermodynamics.
