Abstract
Specific heat capacity of extremely confined water determines its performance in the heat transfer as the sizes of devices decrease to nanoscales. Here, we report the basic data of the specific heat capacity of water confined in narrow graphene nanochannels below 5 nm in height using molecular dynamics simulations. The results show that the specific heat capacity of confined water is size-dependent, and the commensurability effect of the specific heat capacity presents as the confinement decreases to 1.7 nm. The deviation of specific heat capacity of confined water with that of bulk water is attributed to the variation of configuration features, including density distribution and hydrogen bonds, and vibration features, including velocity auto-correlation function and vibrational density of states. This work unveils the confinement effects and their physical mechanisms of the specific heat capacity of nanoconfined water, and the data provided here have wide prospects for energy applications at nanoscales.
Highlights
Specific heat capacity is an important thermophysical property that measures the ability of energy storage of the substance, defined as the amount of heat required to increase the temperature by 1 K of a substrate per unit mass
The different variations of cv and the specific internal energy demonstrate that cv measures the sensitivity of internal energy to temperature but not the value of internal energy (Tombari et al, 2005b), they do have a relationship, which will be discussed in velocity auto-correlation function (VACF) and vibrational density of states (VDOS)
We perform molecular dynamics (MD) simulations to investigate the specific heat capacity of water confined in extremely narrow graphene nanochannels from the aspects of configuration and vibration
Summary
Specific heat capacity is an important thermophysical property that measures the ability of energy storage of the substance, defined as the amount of heat required to increase the temperature by 1 K of a substrate per unit mass. The thermophysical properties of nanoconfined water (Sun et al, 2020), especially specific heat capacity, determines whether it can still function at nanoscales. Tombari et al (2005a), Tombari et al (2005b) investigated the specific heat capacity of water confined in glass nanopores in a mean diameter of 4 nm using calorimetry. They found that the isobaric specific heat capacity deviated from the bulk value and attributed it to the reduction in the density due to the nanoconfinement. Inelastic neutron scattering technique was developed to estimate the specific heat capacity of liquids confined in nanopores (Gautam et al, 2018). Directly experimental measurements of specific heat capacity of nanoconfined water are still limited because of the challenge of precise control and measure of the small amount of water
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