Effect of surface wettability on specific heat capacity of nano-confined liquid

AKMM Morshed and P Das and ZAR Bhuiyan, JOURNAL OF MOLECULAR LIQUIDS, 383, 122115 (2023).

DOI: 10.1016/j.molliq.2023.122115

Equilibrium Molecular Dynamics (EMD) simulations are carried out to investigate the effects of wall wettability and nanogap thickness (h) on the constant volume molar heat capacity (C-v) of liquid argon entrapped between two solid copper walls at a fixed temperature of 100 K. Lennard- Jones (LJ) potential is employed to model the interaction between atoms, with nanogap thickness (h) varying between 0.585 nm to 5.85 nm. To characterize interfacial surface wettability as hydrophobic or hydrophilic, the solid-liquid interaction potential has been altered, and its effect on molar heat capacity (C-v) has been evaluated. Simulation results reveal three key findings. As the surface becomes more hydrophobic (i) both maximum heat capacity (C-v,(max)), and critical nanogap thickness (h(c)) (nanogap thickness at which maximum heat capacity is obtained) decrease; (ii) the range of nanogap thickness where the heat capacity of nanoconfined liquid surpasses that of bulk liquid diminishes; (iii) the heat capacity of nanoconfined liquid tends to match its bulk equivalent. This anomalous behavior of heat capacity with changing wall wettability is explained by variation in both vibrational (mode of phonon transportation) and configurational (density oscillation near the wall, thermal boundary resistance, molecular mobility, etc.) contribution of nanoconfined liquid.

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