The fundamental triple point of substances on the phase diagram: the secret becomes clear

V.V. Brazhkin^†
Vereshchagin Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe shosse 14, Troitsk, Moscow, 108840, Russian Federation

This article analyzes the positions of the triple points of various elementary substances and simple compounds on the phase diagram. Pressures at triple points vary greatly — by 10—12 orders of magnitude for most substances, and in some cases, by 40 orders of magnitude! This enormous spread of values is attributed to the very strong, nearly exponential, dependence of the saturated vapor pressure on the reciprocal temperature near the sublimation and boiling lines. A good correlation has been established between the pressure at the triple point of a substance and the ratio of the temperature at the critical point to the temperature at the triple point. The relationship between the phase diagrams of substances and the position of the triple and critical points on them is examined, along with the effective interparticle interaction potential. The evaporation of solid objects in space conditions is discussed.

Correspondence should be addressed to
Keywords: phase diagrams, triple point, critical point
PACS: 51.30.+i, 64.10.+h, 64.70.Hz (all)
DOI: 10.3367/UFNe.2026.01.040089
URL: https://ufn.ru/en/articles/2026/6/e/
Citation: Brazhkin V V "The fundamental triple point of substances on the phase diagram: the secret becomes clear" Phys. Usp. 69 606–614 (2026)

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Received: 25th, November 2025, revised: 21st, January 2026, accepted: 21st, January 2026

Оригинал: Бражкин В В «Основная тройная точка веществ на фазовой диаграмме: тайное становится явным» УФН 196 649–658 (2026); DOI: 10.3367/UFNr.2026.01.040089

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