Alkoxy-ethanol is highly associating molecule which contains ether (-O-) and hydroxyl (-OH) group in the same molecule. It has both inter- and intra-molecular hydrogen bonding, thus the complex interaction makes it difficult to estimate the thermophysical properties of its fluid mixtures. When simulating the pure alkoxy-ethanol or its mixture system, the positive charge of hydroxyl hydrogen plays an important role because it could form partial hydrogen bonding with both the proton accepters.
The TraPPE and NERD force filed is the two most widely used force fields which provide the robust molecular simulation framework for various thermophysical properties' estimation, especially phase equilibrium study. These two force fields use the united atom based approach to represent the CH, CH2, CH3 groups which enables the transferability of their force field parameters to a wide range of molecular species. With this simulation methodology, coexistence properties can be predicted with relatively high levels of accuracy. Basically these two force fields have very similar energy expression each other, but they don't consider the hydrogen bonding term explicitly in its energy expression. Therefore the effect of hydrogen bonding should be investigated for some specific system such as alkoxy-ethanol and its mixture system.
On this united atom base, the force field parameters of alkoxy-ethanol have been optimized and the molecular structure and coexisting properties of alkoxy-ethanol and its mixture has been studied. The results are compared to simulation results using NERD and TraPPE parameters.
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