ABSTRACT
The application of recent advances in theoretical and computational methods will undoubtedly play a
significant role in the design of new materials. This is especially true for materials such as highly efficient
thermoelectrics. Even though thermoelectric effects were discovered almost two centuries ago, there
remain major challenges to increasing the efficiency of thermoelectric devices. The basic challenge in
the development of new thermoelectric materials is to maximize the thermoelectric figure-of-merit,
ZT ¼ sS
T=k, where s is the electrical conductivity, k is the thermal conductivity, and S is the Seebeck
coefficient or thermopower. This dimensionless quantity provides a measure of the efficiency or
performance of a thermoelectric material. Since the optimization of the Seebeck coefficient for any
material will involve the appropriate modification of its electronic properties, a fundamental
understanding of the electronic band structure will be a valuable, if not essential requirement if the
current upper limit of ZT is to be increased significantly. The optimization of the figure-of-merit appears
to be a challenging problem since the three properties that determine this quantity are closely connected.
For example, the ratio s=k is limited by the ability to reduce the thermal conductivity k to its limiting
value by reducing the contribution from lattice thermal conductivity to a minimum. The remaining
contribution to the thermal conductivity is electronic and this is approximately related to the electrical
conductivity s by the Wiedemann-Franz law. The Seebeck coefficient is also partially determined by the
electrical conductivity. The objective therefore of theoretical studies is to find ways, in principle, to
optimize the figure-of-merit by suggesting materials with optimized electronic band structures and
thermal transport properties. There is no well-defined theoretical limit to the figure-of-merit and this
provides a challenge for theoreticians and experimentalists alike to search for ways to increase its value. It
has been pointed out
