The calculated scalar-averaged κ latt of the four Ge chalcogenides is shown in Fig. . Given that the ultra-low lattice thermal conductivity of SnSe is a key contributor to its high thermoelectric performance, we also compare our predictions to similar calculations on SnS and SnSe. The κ latt span a range of 0.82 -1.71 W m -1 K -1 at 800 K (Table ) and fall in the order of R3m GeSe > Pnma GeS ≈ R3m GeS > Pnma GeSe ≈ Pnma SnS > Pnma SnSe. The orthorhombic Ge chalcogenides therefore have larger κ latt than the Sn analogues, but Pnma GeSe has a κ latt comparable to SnS.