  We develop a procedure to determine the portion of exact Hartree-Fock
exchange interaction contained in a hybrid density functional to treat the
range of electronic correlation governing the physics of a system as a function
of a thermodynamical parameter. This includes systems that depend on physical
parameters accessible to experiment (i.e., temperature, pressure, composition,
etc.) or those composed of two or more materials such as heterostructures and
interfaces. This approach is applied to LaMnO$_3$ where for the first time we
are able to simulate the high temperature insulator-to-metal transition (IMT)
and observe a half-metallic orbital disorder ferromagnetic state using density
functional theory. In particular, we show that the softening of the
\textit{Q$_2$} Jahn-Teller mode plays a central role in driving the IMT. These
findings are likely to motivate the investigation of heterostructures and bulk
materials that contain a range of electronic correlation in similar material
systems.
