Abstract
The clustering of sulphuric acid with base molecules is one of the main
pathways of new-particle formation in the Earth's atmosphere. First step
in the clustering process is likely the formation of a (sulphuric acid)1(base)1(water)n cluster. Here, we present results from direct first-principles molecular dynamics collision simulations of (sulphuric acid)1(water)0, 1 + (dimethylamine) → (sulphuric acid)1(dimethylamine)1(water)0, 1
cluster formation processes. The simulations indicate that the sticking
factor in the collisions is unity: the interaction between the
molecules is strong enough to overcome the possible initial non-optimal
collision orientations. No post-collisional cluster break up is
observed. The reasons for the efficient clustering are (i) the proton
transfer reaction which takes place in each of the collision simulations
and (ii) the subsequent competition over the proton control. As a
consequence, the clusters show very dynamic ion pair structure, which
differs from both the static structure optimisation calculations and the
equilibrium first-principles molecular dynamics simulations. In some of
the simulation runs, water mediates the proton transfer by acting as a
proton bridge. In general, water is able to notably stabilise the formed
clusters by allocating a fraction of the released clustering energy.
| Original language | English |
|---|---|
| Journal | Molecular Physics |
| Volume | 112 |
| Issue number | 15 |
| Pages (from-to) | 1979-1986 |
| Number of pages | 8 |
| ISSN | 0026-8976 |
| DOIs | |
| Publication status | Published - 3 Aug 2014 |