**Origins of thermal conductivity changes in strained crystals**

KD Parrish and A Jain and JM Larkin and WA Saidi and AJH McGaughey, PHYSICAL REVIEW B, 90, 235201 (2014).

DOI: 10.1103/PhysRevB.90.235201

The strain-dependent phonon properties and thermal conductivities of a
soft system **Lennard-Jones (LJ) argon** and a stiff system (silicon
modeled using first-principles calculations) are predicted using lattice
dynamics calculations and the Boltzmann transport equation. As is
commonly assumed for materials under isotropic strain, the thermal
conductivity of LJ argon decreases monotonically as the system moves
from compression into tension. The reduction in thermal conductivity is
attributed to decreases in both the phonon lifetimes and group
velocities. The thermal conductivity of silicon, however, is constant in
compression and only begins to decrease once the system is put in
tension. The silicon lifetimes show an anomalous behavior, whereby they
increase as the system moves from compression into tension, which is
explained by examining the potential energy surface felt by an atom. The
results emphasize the need to separately consider the harmonic and
anharmonic effects of strain on material stiffness, phonon properties,
and thermal conductivity.

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