Comment on “Thermal expansion and phase stability of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>B</mml:mi> <mml:msub> <mml:mi mathvariant="normal">F</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> ( <

The title paper [Phys. Rev. B 110, 064104 (2024)] examines the negative thermal expansion and phase transitions in ${\mathrm{ScF}}_{3}$ and related materials through density functional theory calculations. The calculations of negative thermal expansion in the noncubic materials are in error for two important reasons. First, these calculations use a formulation of Gr"uneisen theory that is only applicable to isotropic systems. Not only is this formulation wrong, but the choice of volume change in the derivatives of phonon frequencies is automatically arbitrary. A second error is the neglect of LO/TO splitting of the phonon frequencies at zero wave vector, which in the software chosen by the authors leads to an error that spreads across the Brillouin zone. These are both common errors in the literature, which we wish to highlight so that future authors can perform these calculations correctly. We further make two comments on the interpretation of these results. First, in systems that show phase transitions, the thermal expansion is likely dominated by spontaneous strains associated with the phase transition and not through a tension-effect mechanism. Finally, we point out that negative thermal expansion in ${\mathrm{ScF}}_{3}$ is much better understood than acknowledged in the title paper. Indeed, on the basis of recent work, we can easily and automatically understand why the negative thermal expansion would be much reduced, should the thermal expansion be associated with a tension effect, in related materials that are distorted as a result of a displacive phase transition.