Molecular Dynamics Investigations of Dibutyl-phosphoric Acid—Parameterization and Dimerization

Abstract

A reparameterized molecular dynamics force field for dibutyl-phosphoric acid (HDBP) has been developed. Parameterization was done using the general Amber force field, as a starting point. The density and dipole moment of bulk phase simulations compare well to that of known experimental values, and the heat of vaporization is comparable to an estimated empirical value. All values have been optimized to within 4%. The newly optimized force field was validated against the self-diffusion coefficient, matching experimental data to within 18%, which is a significant improvement compared to the nonoptimized force field. Further, a potential of mean force study was carried out to understand the behavior of hydrogen bonds in HDBP dimers. This required the determination of hydrogen bonding criteria that captures the behavior of the HDBP dimer and is reported in this work as well.

Self-Assembly of Hydrogen-Bonded Cage Tetramers of Phosphonic Acid

“…We have shown experimentally that R 2 POOH and (RO) 2 POOH acids predominantly form cyclic trimers in CDF 3 /CDF 2 Cl mixtures. It should be noted, however, that in the gas phase, several phosphinic and phosphoric acids most probably form cyclic dimers, as it was discussed in [17,18] and supported by numerous quantum-chemical calculations [19][20][21][22][23][24][25][26]. In crystal state, phosphinic and phosphoric acids form either cyclic dimers or infinite chains, see e.g., [27][28][29][30][31].…”