The binding of Ca 2+ to anionic groups of lipid molecules leads to a reduction in membrane surface area and an increase in membrane thickness. Notably, the effect is more signiicant for bilayers containing negatively charged lipid molecules. As a consequence, the acyl chains become more ordered, which may facilitate phase transitions. Our results also showed that these indings are rather robust, irrespective of the speciic ion model and parameters adopted in the MD simulations.