This study investigates changes in the morphology of portlandite (Ca(OH)₂) in the presence of different ions using both experimental and atomistic simulation techniques. Experimental results show that the presence of chlorides and nitrates leads to facetted particles with a similar shape, while sulfates result in hexagonal platelet morphology and silicates lead to irregular aggregates. Atomistic simulations validate these observations and reveal that the presence of water stabilizes the [20.3] surface, influencing the morphology. The relative surface energies of the [00.1], [10.0], and [20.3] surfaces were calculated, showing that sulfate ions increase the relative surface energy of these surfaces. The simulations also show that the [20.3] surface, which has high energy in vacuum, is stabilized by water, explaining its appearance in experimental observations. The study highlights the significant influence of different ions on portlandite morphology and growth, with silicates having a particularly strong effect. Atomistic simulations provide insights into the interfacial energies and surface properties of portlandite in water and vacuum, supporting the experimental findings and offering a deeper understanding of the mechanisms behind the observed morphological changes.This study investigates changes in the morphology of portlandite (Ca(OH)₂) in the presence of different ions using both experimental and atomistic simulation techniques. Experimental results show that the presence of chlorides and nitrates leads to facetted particles with a similar shape, while sulfates result in hexagonal platelet morphology and silicates lead to irregular aggregates. Atomistic simulations validate these observations and reveal that the presence of water stabilizes the [20.3] surface, influencing the morphology. The relative surface energies of the [00.1], [10.0], and [20.3] surfaces were calculated, showing that sulfate ions increase the relative surface energy of these surfaces. The simulations also show that the [20.3] surface, which has high energy in vacuum, is stabilized by water, explaining its appearance in experimental observations. The study highlights the significant influence of different ions on portlandite morphology and growth, with silicates having a particularly strong effect. Atomistic simulations provide insights into the interfacial energies and surface properties of portlandite in water and vacuum, supporting the experimental findings and offering a deeper understanding of the mechanisms behind the observed morphological changes.