All porous materials deform during fluid adsorption. Although for most of the materials the experimentally observed strains are small, this phenomenon has a number of important applications, including sensors , actuators , CO2 sequestration . In addition to those, adsorption-induced deformation has potential for characterization of porous materials because deformation is very sensitive to the pore sizes. In recent years there has been a major progress in developing theory of adsorption-induced deformation [4-6]. However, these studies were focused on calculating the pressure in the fluid phase, while the stresses in the solid phase were not considered explicitly. The current work fills this gap, presenting the electronic-structure density functional theory modeling of the dry and wet silica surfaces. In addition to the information on change of the surface energy with fluid adsorption, our calculations show how the components of surface stress tensor change. This change is the key parameter necessary for quantitative understanding of the adsorption-induced deformation phenomenon.
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