The geometric configuration and electronic structure of C-40, Nb@C-40(
+) and La@C-40(+) were studied by using quantum chemical ab initio met
hod. The most stable configuration of C-40 was found to possess D-2 sy
mmetry. Nb and La atoms of Nb@C-40(+) and La@C-40(+), were inside the
C-40 cage, forming endohedral metallofullerenes. Binding energy of C-4
0 was larger than those of M@C-40(+)(M=Nb, La).