Calculation of mode Gruneisen parameters made simple

Gruneisen parameters measure the degree of anharmonicicy of a material.
These parameters can be used to calculate the coefficient of thermal expansion,
as well as the thermal conductivity of a material. The existing method
to calculate mode Gruneisen parameters relies on the (quasi-)harmonic approximation,
and the numerical differentiation of phonon frequencies computed at different
volumes (through the use of energy schemes based on either classical force fields
or a first principles approach). Here we present a new method to calculate mode
Gruneisen parameters. This method involves two steps. First, the
calculation of the harmonic frequencies at only the equilibrium volume of
a material. Second, for each normal mode, a few self-consistent
field calculations are needed to calculate the corresponding
mode Gruneisen parameter. In this talk, we discuss the conceptual basis of
the new method, its technical implementation and validation, its advantages
and disadvantages, and selected applications. In particular, our method in combination
with a density functional theory approach is used to calculate
mode Gruneisen parameters and the coefficient of thermal expansion of
silicon and aluminum.