I am currently performing molecular dynamics simulations of water/ice and would like some intuition behind some of the results I am seeing. For context, I am using the water model described in this paper. A quick summary of the water model is that it used SCAN-DFT to create configurations of ice and water at ambient conditions, and then the potential energy surface was more widely explored using deep potential molecular dynamics. I am seeing some results that I am currently attributing to how DFT calculations are often hand wavey when it comes to water in two distinct phase transitions. The first is the melting of ice where I have found the melting point for this potential to be 320K. The second phase transition is the amorphization of ice 1h under pressure. This amorphization is expected to occur at 10kbar, however, I am only seeing it at 22.5kbar. With this all in mind, I have proposed that maybe this effect is due the DFT calculations the water model is built from. I do not know much about DFT at all, but I am aware that SCAN-DFT is supposed to overestimate the strength of hydrogen bonding networks. I understand the melting point discrepancy is due to this effect, but am unsure about the pressure discrepancy. So this all leaves me with 2 closely related questions...
- Why does SCAN-DFT overestimate the strength of hydrogen bonding networks?
- Would the artificially stronger hydrogen bonds be responsible for the discrepancy in the pressure needed for the ice 1h to HDA ice phase transition?
