  C60 fullerene has been studied extensively, as it is considered to be a good
candidate for building single-molecule junctions. Here, we theoretically
demonstrate that the conductance of single-molecule junctions based on a newly
discovered molecule, borospherene (B40), is comparable to that for the
C60-based junction with its more delocalized {\pi} electrons. The charge
injection efficiency in the B40-based junction is improved, as up to 7 atoms in
direct contact with the electrode are possible in the Au-B40-Au junction.
Interestingly, a higher number of atoms in direct contact with the electrode
does not result in a higher number of conduction channels because of the unique
chemical bonding in the B40 molecule, without two-center two- electron bonds.
The transport properties of Au-B40-Au junctions can be proved by doping. With a
Ca, Sr, or Y atom encapsulated into the B40 cage, the conductance at zero bias
increases significantly. Moreover, our calculations show that the lowest
unoccupied molecular orbital dominates the low-bias transport, as the
thermopower in these junctions is negative. Our study indicates that B40 is an
attractive new platform for designing highly conductive single-molecule
junctions for future molecular circuits.
