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Abstract
The [rho] value of single-crystalline SnSe estimated from the powder X-ray diffraction studies were in the range 6.13-6.18 g cm-3 (Joint Committee on Powder Diffraction Standards (JCPDS) card numbers 01-089-232, 01-089-233 and 01-089-235)2, while neutron diffraction studies3 reported a [rho] value of about 6.18 g cm-3 (JCPDS card number 01-071-3877). Thermoelectricians have long aimed to optimize ZT by reducing [kappa], and ref. 1 reported exceptionally low thermal conductivity. [...]the sole aim of this Comment is to correct the scientific record by stating that the ultralow [kappa] value reported in ref. 1 is not intrinsic to fully dense single-crystalline SnSe. A single crystal, by definition, must have an experimentally measured density that is close to 100% of the theoretical density. [...]the SnSe samples of ref. 1 cannot be classified as single crystalline and the thermal conductivity and figure of merit values for SnSe presented in ref. 1 are not intrinsic to single-crystalline SnSe.