Molar Heat Capacity of Cu Ѳ= 240 K Fit uses Einstein vibrational frequency of 5 x 1012 s-1 Cv  T3 Temp (K) Fig. 9.1 from D. Tabor, Gases, Liquids and Solids (1991) Cambridge Univ Press.

Comparisons of Molar Heat Capacity for Several Metals ● = Ag; ѲD = 215 K  = Pb; ѲD = 88 K X = C; ѲD = 1860 K Ο = C; ѲD = 315 K Fig. 9.4 from D. Tabor, Gases, Liquids and Solids (1991) Cambridge Univ Press.

Molar heat capacities of various gases at 25 °C From Tipler’s Physics

Molar Heat Capacity of Iron Cv ~ T3 From Tipler’s Physics