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In a recent paper [arXiv:0804.3569], Takatoshi Nomura {\it et al.} reported astructural phase transition near 150 K in LaOFeAs and used space group "Cmma"to describe their X-ray diffraction data. However, they did not discuss howtheir proposed structure compares with the early neutron study by Cruz {\it etal.}[arXiv:0804.0795] where the low temperature structure of LaOFeAs wasdescribed by space group "P112/n". This caused some confusion, suggesting thatthere may be some disagreement on the low temperature structure of LaOFeAs asevidenced by several inquiries that we received. Here we show that the proposedstructures from x-ray and neutron diffraction are basically identical. The P2/c(i.e., P112/n) cell becomes the primitive cell of the Cmma cell when thez-coordinate of the oxygen and iron are assumed to be exactly 0 and 0.5 (thesenumbers were reported to be -0.0057 and 0.5006 in neutron study). Ourfirst-principles total-energy calculations suggest that the oxygen and ironatoms prefer to lie on the z=0 and 1/2 plane, respectively, supporting Cmmasymmetry. However it is more convenient to describe the structural distortionin the primitive P2/c cell which makes it easier to see the connection betweenthe high (i.e., P4/nmm) and low temperature structures.

A Brief Comment on the Low-Temperature Structure of LaOFeAs