How to Estimate the Melting Point of a Potential

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The melting point of a solid crystalline substance is the temperature at which a solid sample changes into a liquid. This temperature is influenced by a number of different factors including crystal purity, water content, and electronegativity differences between the two components.

Melting Point Depression

Melting point depression is the reduction of the melting point of an impure material compared to that of a pure one, due to contaminations that weaken lattice forces within a solid crystalline substance. This phenomenon can be used to identify the purity of a mixed substance.

How to Estimate the Melting Point of a Potential

To estimate a melting point, it is necessary to first calculate an approximate value for Tem. This is typically performed by heating up a solid and cooling down a liquid. However, this method is computationally expensive and the overheating/undercooling boundaries may not be accurate.

Step 1: Prepare a solid sample N x N x N as shown in Fig 1. Then roughly estimate Tem by performing MD simulations using this solid sample.

If the first estimated temperature, Tem, is much lower than the actual melting point, full solidification may occur during the simulations. This can be avoided by monitoring the interface structures.

Second, if the difference between the predicted melting point, Tpm, and the estimated temperature, Tem, is larger than a certain convergence criterion D1, a further loop from step 2 to 4 needs to be performed with a new temperature estimate, Tem=Tpm.