We have simulated by ab initio constant pressure molecular dynamics the solid-state polymerization of acetylene recently observed experimentally in the pressure range 3.5–14 GPa. We have found a massive polymerization only at much higher pressure (25 GPa). However, we have also found that a triplet exciton self-trapped on a single, cis-bent molecule in crystalline acetylene is a very effective polymerization seed at lower pressure ( $<9\mathrm{}$ GPa), much closer to the experimental threshold. Therefore, we propose that the polymerization observed experimentally is possibly catalyzed by a similar seed. We predict that injection of triplet excitons would greatly enhance the polymerization rate.

• Received 22 May 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2008