ANISOTROPIC A-C-H FROM COMPRESSION OF POLYACETYLENE

We have simulated the transformation of crystalline trans-polyacetylen e into alpha-C:H under pressure by constant pressure ab initio molecul ar dynamics. Polyacetylene undergoes a gradual saturation of C-C bonds via chain interlinks, ending up at similar to 59 GPa with alpha-C:H c ontaining 80% sp(3) carbon atoms. The sp(2) --> sp3 conversion is irre versible and does not reverse by returning to zero pressure. The final alpha-C:H is a wide gap insulator and, at variance with the conventio nally generated alpha-C:H, is highly anisotropic keeping some memory o f the original polyacetylene chain axis.