Results of theoretical calculations at 0 K on the two known structures of solid acetylene using the modified Gordon–Kim plus damped dispersion model are reported. The lattice energy of the low temperature C m c astructure is compared to that of the high temperature P a3 structure at zero pressure and found to be slightly less stable, though a very small pressure (about 0.25 kbar) stabilizes the C m c astructure relative to the P a3 structure. Agreement between the experimental structure and energy for the C m c astructure and our present results is good. Structural properties of the C m c astructure were calculated to 100 kbar as well as the pressure dependence of the A g libron mode. A possible high‐pressure path for the polymerization of solid C m c a acetylene that would lead to a well‐ordered polymer was proposed, but calculations of C–C distances suggest that a more cross‐linked product would be favored.