Negative thermal expansion in hexagonal VF₃ predicted by first_principles calculation

Searching negative thermal expansion (NTE) materials is challenging. Herein, hexagonal VF₃ is predicted as a new NTE material for the first time. VF₃ displays NTE property in the temperature range from 0 to 380 K, and the minimum NTE coefficient(α) is approximately −4.68 × 10⁻⁶ K⁻¹ at 120 K. The NTE mechanism was ascribed to the vibrations of F atom with larger atomic displacement parameters, which dominates the negative Grüneisen parameters. The difference of minimum NTE coefficient between VF₃ and TiF₃ might be caused by their different chemical bond strength between Ti–F and V–F. This research provides a deeper understanding between NTE and crystal structure.