We study melting in a two-dimensional system of classical particles with Gaussian-core interactions in disordered environments. The pure system validates the conventional two-step melting with a hexatic phase intervening between the solid and the liquid. This picture is modified in the presence of pinning impurities. A random distribution of pinning centers forces a hexaticlike low-temperature phase that transits into a liquid at a single melting temperature $T_{\mathrm{m}}^{\mathrm{RP}}$. In contrast, pinning centers located at randomly chosen sites of a perfect crystal anchor a solid at low temperatures which undergoes a direct transition to the liquid at $T_{\mathrm{m}}^{\mathrm{CP}}$. Thus, the two-step melting is lost in either case of disorder. We discuss the characteristics of melting depending on the nature of the impurities.

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• Classical statistical mechanics
• Exotic phases of matter
• Topological defects
• 2-dimensional systems
• Complex fluids
• Disordered systems
• Molecular dynamics