Data for the sorption and interaction of alcohols with the coal suggested Upper Freeport coal has a large number of micropores into which relatively bulky reagents could diffuse only marginally; micropores may be molecular voids in the aggregated. The irreversible structural relaxation observed on differential scanning calorimeter (DSC) thermograms at 350 degreesC is probably very similar in nature to that caused by extraction with highly efficient mixed solvents such as carbon disulfide/N-methyl pyrrolidinone (CS2/NMP). Upper Freeport coal must be greatly relaxed (swollen) before solvents have access. A molecular dynamics simulation of relaxation at several temperatures was carried out on a model structure for the aggregated coal. A large change in the volume of the model structure was found between 350 degreesC and 400 degreesC, the region in which the irreversible peak was observed in the DSC thermograms. Moreover, in agreement with the experimental results, the structural changes caused by "heating" in the simulation were not reversible. These results suggested that irreversible structural relaxation caused by heating is the result of thermal stabilization of the strained structure of the raw coal.