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On the Chain-Melted Phase of Matter

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Original languageEnglish
JournalProceedings of the National Academy of Sciences
Early online date11 Apr 2019
DOIs
Publication statusPublished - 21 May 2019

Abstract

Various single elements form incommensurate crystal structures under
pressure, where a zeolite-type “host" sublattice surrounds a
“guest" sublattice comprising 1D chains of atoms. On “chain melting",
diffraction peaks from the guest sublattice vanish, while those
from the host remain. Diffusion of the guest atoms is expected to be
confined to the channels in the host sublattice, which suggests 1D
melting. Here, we present atomistic simulations of Potassium to investigate
this phenomenon, and demonstrate that the chain-melted
phase has no long-ranged order either along or between the chains.
This 3D disorder provides the extensive entropy necessary to make
the chain melt a true thermodynamic phase of matter, yet with the
unique property that diffusion remains confined to 1D only. Calculations
necessitated the development of an interatomic forcefield using
machine learning, which we show fully reproduces Potassium’s
phase diagram, including the chain-melted state and 14 known phase
transitions.

ID: 81522029