Investigation of the role of polysaccharide in the dolomite growth at low temperature by using atomistic simulations

TL;DR

This study uses atomistic simulations to explore how polysaccharides influence water dehydration on dolomite surfaces at low temperatures, revealing that oligosaccharides can lower the dehydration barrier by forming specific configurations.

Contribution

It demonstrates that oligosaccharides can reduce the dehydration barrier on dolomite surfaces, highlighting the role of molecular conformation and hydrophobic interactions in mineral growth.

Findings

Oligosaccharides decrease dehydration barrier by 0.7-1.1 kcal/mol.

Monosaccharides have no significant effect.

Bridge-shaped oligosaccharide configurations facilitate barrier reduction.

Abstract

Dehydration of water from surface Mg2+ is most likely the rate-limiting step in the dolomite growth at low temperature. Here, we investigate the role of polysaccharide in this step using classical molecular dynamics (MD) calculations. Free energy (potential of mean force, PMF) calculations have been performed for water molecules leaving the first two hydration layers above the dolomite (104) surface under the following three conditions: without catalyst, with monosaccharide (mannose) and with oligosaccharide (three units of mannose). MD simulations reveal that there is no obvious effect of monosaccharide in lowering the dehydration barrier for surface Mg2+. However, we found that there are metastable configurations of oligosaccharide, which can decrease the dehydration barrier of surface Mg2+ by about 0.7-1.1 kcal/mol. In these configurations, the molecule lies relatively flat on the surface and forms a bridge shape. The hydrophobic space near the surface created by the non-polar -CH groups of the oligosaccharide in the bridge conformation is the reason for the observed reduction of dehydration barrier.