  The critical properties of the finite temperature Mott endpoint are
drastically altered by a coupling to crystal elasticity, i.e., whenever it is
amenable to pressure tuning. Similar as for critical piezoelectric
ferroelectrics, the Ising criticality of the electronic system is preempted by
an isostructural instability, and long-range shear forces suppress microscopic
fluctuations. As a result, the endpoint is governed by Landau criticality. Its
hallmark is thus a breakdown of Hooke's law of elasticity with a non-linear
strain-stress relation characterized by a mean-field exponent. Based on a
quantitative estimate, we predict critical elasticity to dominate the
temperature range DeltaT/Tc ~ 8% close to the Mott endpoint of
kappa-(BEDT-TTF)2X.
