ABSTRACT
The microcanonical ensemble verifies the conditions of application of the fundamental postulate, valid for isolated systems. As such, it has allowed the development of a statistical approach (Chapter 2) and the recovery of thermodynamics by offering a microscopic interpretation of entropy in terms of number of accessible microstates (Chapter 3). Conceptually simple, microcanonical conditions are ideal conditions that are difficult to implement in practice: a system cannot be perfectly isolated and energy is a delicate quantity to control experimentally. In general, natural or laboratory systems are in contact with an external medium imposing thermodynamic conditions (temperature, pressure), such as the Earth’s atmosphere or a thermostat whose temperature is chosen by an experimentalist.
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