Modeling gas-phase hydration of the sulfuric acid in the Earth's atmosphere
Moscow State Technological University "STANKIN" Russia, 127055, Moscow, ul. Vadkovsky per. 1, Tel: (+ 7 499) 972-95-00; E-mail: firstname.lastname@example.org
A computational experiments were performed to determine the structure and properties of gas-phase molecular clusters (H2SO4)(H2O)n, n = 0-6 . Conformational search was carried out for 64 isomers with 15 density functionals and 7 basis sets. The Gaussian 09 suite of programs was used to calculate properties of the hydrated clusters.
New collective and scaling effects were revealed and described in some detail. In particular, we find that the location of global and local minima on the Gibbs free energy scale and associated entropic effects can lead to a moderately strong dependence of the average dipole moment of ensembles of isomers on temperature. It was also shown that the scaling effects can be significant. For the example, in the case of H2SO4-H2O hydrates, the difference in the density between clusters and macroscopic binary liquids of identical composition, which may be as high as 15-20%, decreases with the growing hydration number signifying the transition of the cluster to macroscopic liquid.
It was also shown that the conventional approach to benchmarking DFT and ab initio methods by comparing changes in electronic energies or enthalpies , is not applicable in the case, when the accuracy of predictions of the cluster stability by different methods is examined. A new approach, which is based on the comparison of the theoretical and experimental Gibbs energy changes and allows to choose methods for accurately calculating the thermodynamic properties of clusters and nanoparticles, has been proposed and validated .
The work was supported by the Ministry of Education and Science of the Russian Federation, project No. 1.7706.2017 / BC, and RFBR, grant No. 15-08-4969a.
1. Nazarenko E.S. Features of modeling the formation of gas-phase hydrates in the atmosphere. // Natural and technical sciences. 2017. № 9. 83-91