The adsorption mechanism of calcium ion is a piece of important information for understanding the performance of quartz activation. In this work, the adsorption of calcium ion on quartz (101) surface in aqueous was studied through DFT calculations. The effective coordination number of calcium ion and the corresponding coordination structure in aqueous were simulated to confirm activation components. Meanwhile, adsorption energies of three sites (top, bridge and hollow) on quartz surface were calculated to investigate the preferred adsorption position, while adsorption structure of calcium ion in aqueous was also determined by DFT calculation. PDOS projections and Mulliken populations were carried out to explore the Ca-O bonding nature. The analytical results indicated that the formation of Ca-(Oq) (calcium ion in aqueous and O atom on quartz surface) bond and hydration process of quartz surface were both closely related to calcium ion adsorption on the quartz surface. The simulated adsorption structures were accordant with the experimental data of the FT-IR spectra analysis. (C) 2018 Elsevier B.V. All rights reserved.