Structure and electronic properties of highly charged C_(60) and C_(58) fullerenes

摘要

We present a theoretical study of the structure and electronic properties of positively charged C_(60)~(q+) and C_(58)~(q+) fullerenes (q=0-14).Electronic energies and optimum geometries have been obtained using density-functional theory with the B3LYP functional for exchange and correlation.We have found that closed- and semiclosed-shell C_(60)~(q+) ions (q-0,5,and 10) preserve the original icosahedral symmetry of neutral C_(60).For other charges,significant distortions have been obtained.The C_(58)~(q+) fullerenes are,in general,less symmetric,being C_(58)~(8+) the closest to the spherical shape.Most C_(60)~(q+) fullerenes follow Hund's rule for spin multiplicity,while most C_(58)~(q+) fullerenes are more stable with the lowest spin multiplicity.The calculated ionization potentials for both kinds of fullerenes increase almost linearly with charge,except in the vicinity of C_(60)~(10+) and C_(58)~(8+).We have also explored the region of the potential-energy surface of C_(60)~(q+) that leads to asymmetric fission.Minima and transition states corresponding to the last steps of the fission process have been obtained.This has led us to conclude that,for 3<=q<=8,C_2~+ emission is the preferred fragmentation channel,whereas,for higher q values,emission of two charged atomic fragments is more favorable.The corresponding fission barrier vanishes for q>14.