  The thermal conductivity of a nanostructure is sensitive to its dimensions. A
simple analytical scaling law that predicts how conductivity changes with the
dimensions of the structure, however, has not been developed. The lack of such
a law is a hurdle in "phonon engineering" of many important applications. Here,
we report an analytical scaling law for thermal conductivity of nanostructures
as a function of their dimensions. We have verified the law using very large
molecular dynamics simulations.
