On the heat capacity of Ti 3GeC 2

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In this paper, we report experimental data of the heat capacities, c p , of bulk polycrystalline samples of Ti 3GeC 2 in the 3–260 K temperature range. The results obtained are compared with those on Ti 3SiC 2. The c p results are analyzed using the Debye and Einstein models and are compared to the heat capacities values calculated from first principles. At temperatures up to 10 K the main contributors to c p are electrons with γ = 6.5 (mJ/mol K 2) and phonons with a Debye temperature θ D of 556 K. In that temperature range only four atoms of the six in a formula unit—most likely one Ge and three Ti atoms—contribute to c p . In the 10–120 K temperature range excellent fits were obtained using a θ D of 513 K and an optical mode with an Einstein temperature θ E of 139 K. For T > 120 K, five additional optical modes with θ E = 870 K are required to properly fit the experimental results. The ab initio calculations throughout the temperature range (4–1500 K) show reasonably good agreement with the experimental data obtained particularly at low temperatures.