## Abstract

This paper determines the thermodynamic phase diagram of the EXP system of particles interacting by the purely repulsive exponential pair

potential. The solid phase is face-centered cubic (fcc) at low densities and pressures. At higher densities and pressures, the solid phase is bodycentered cubic (bcc) with a re-entrant liquid phase at the highest pressures simulated. The investigation first identifies the phase diagram at

zero temperature at which the following four crystal structures are considered: fcc, bcc, hexagonal close packed, and cubic diamond. There is a

T = 0 phase transition at pressure 2.651 × 10−3 with the thermodynamically stable structure being fcc below and bcc above this pressure. The

densities of the two crystal structures at the phase transition are 1.7469 × 10−2

(fcc) and 1.7471 × 10−2

(bcc). At finite temperatures, the fcc–

bcc, fcc-liquid, and bcc-liquid coexistence lines are determined by numerical integration of the Clausius–Clapeyron equation and validated

by interface-pinning simulations at selected state points. The bcc-fcc phase transition is a weak first-order transition. The liquid-fcc–bcc triple

point, which is determined by the interface-pinning method, has temperature 5.9 × 10−5

and pressure 2.5 × 10−6

; the triple-point densities

are 1.556 × 10−3

(liquid), 1.583 × 10−3

(bcc), and 1.587 × 10−3

(fcc).

potential. The solid phase is face-centered cubic (fcc) at low densities and pressures. At higher densities and pressures, the solid phase is bodycentered cubic (bcc) with a re-entrant liquid phase at the highest pressures simulated. The investigation first identifies the phase diagram at

zero temperature at which the following four crystal structures are considered: fcc, bcc, hexagonal close packed, and cubic diamond. There is a

T = 0 phase transition at pressure 2.651 × 10−3 with the thermodynamically stable structure being fcc below and bcc above this pressure. The

densities of the two crystal structures at the phase transition are 1.7469 × 10−2

(fcc) and 1.7471 × 10−2

(bcc). At finite temperatures, the fcc–

bcc, fcc-liquid, and bcc-liquid coexistence lines are determined by numerical integration of the Clausius–Clapeyron equation and validated

by interface-pinning simulations at selected state points. The bcc-fcc phase transition is a weak first-order transition. The liquid-fcc–bcc triple

point, which is determined by the interface-pinning method, has temperature 5.9 × 10−5

and pressure 2.5 × 10−6

; the triple-point densities

are 1.556 × 10−3

(liquid), 1.583 × 10−3

(bcc), and 1.587 × 10−3

(fcc).

Originalsprog | Engelsk |
---|---|

Artikelnummer | 174501 |

Tidsskrift | Journal of Chemical Physics |

Vol/bind | 2019 |

Udgave nummer | 150 |

Antal sider | 9 |

ISSN | 0021-9606 |

DOI | |

Status | Udgivet - 3 maj 2019 |