Abstract
The noble elements constitute the simplest group of atoms. At low temperatures or high pressures, they freeze into the face-centered cubic (fcc) crystal structure (except helium). This paper investigates neon, argon, krypton, and xenon by molecular dynamics using the simplified atomic potentials recently proposed by Deiters and Sadus [J. Chem. Phys. 150, 134504 (2019)], which are parameterized using data from accurate ab initio quantum-mechanical calculations by the coupled-cluster approach at the single-double-triple level. We compute the fcc freezing lines and find good agreement with the empirical values. At low pressures, predictions are improved by including many-body corrections. Hidden scale invariance of the potential-energy function is established by showing that mean-squared displacement and the static structure factor are invariant along the lines of constant excess entropy (isomorphs). The isomorph theory of melting [Pedersen et al., Nat. Commun. 7, 12386 (2016)] is used to predict from simulations at a single state point the freezing line's shape, the entropy of melting, and the Lindemann parameter of the crystal at melting. Finally, our results suggest that the body-centered cubic crystal is the thermodynamically stable phase at high pressures.
Highlights
We investigate the noble elements neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) using a potential proposed recently from accurate ab initio calculations
We find that the energy surface obeys hidden scale invariance in the investigated part of the phase diagram and show how this fact can be used to predict the shape of the melting lines
We investigate below the simplified ab initio atomic potential (SAAP) recently suggested by Deiters and Sadus
Summary
The thermodynamic and transport properties of condensed matter systems are determined by their potential-energy functions.. For a class of systems, the potential-energy function exhibits “hidden scale invariance,” making the phase diagram effectively one dimensional; density and temperature collapse into a single parameter.. We investigate the noble elements neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) using a potential proposed recently from accurate ab initio calculations.. We investigate below the simplified ab initio atomic potential (SAAP) recently suggested by Deiters and Sadus.24 This potential is parameterized for the noble elements Ne, Ar, Kr, and. The exponential repulsive (EXP) pair potential 4 ⋅ 105 exp(−12x) (red dashed lines) approximates well the SAAP at short distances. This is consistent with the interpretation of high-pressure compression experiments, the so-called shock Hugoniots..
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