  Ab initio calculations show that the conductance of short monatomic carbon
chain can be dramatically modified by adhering a single H, N, or O atom to the
chain. For example, the conductance of the pristine chain gets about two orders
of magnitude smaller if an H atom is adhered to the chain. By a statistical
model, the structure of the carbon chain with the single atom adhered is found
to be quite stable at room temperature, indicating that the method can be used
to tune the conductance of monatomic carbon chain.
