For common materials like many metals and compounds, the thermal expansion coefficient is inversely proportional to the melting point. In particular, for metals the relation is: α α ≈ ≈ 0.020 T m for halides and oxides α α ≈ ≈ 0.038 T m − − 7.0 ⋅ ⋅ 10 − − 6 K − − 1