Introduction
Study rates at which various processes occur
Complexity of problem reduced by introducing approximations such as assumption of local equilibrium.
Knowledge of kinetics leads to prediction of rates
Mechanisms of change are important in determining kinetics
1.1 Thermodynamics and Kinetics
Two broad topics in the study of materials science:
- Thermodynamics: study of equilibrium states in which state variables of a system do not change with time.
- Kinetics: study of the rates at which systems that are out of equilibrium change under the influence of various forces.
Thermodynamics provides information about the final state of a system
Kinetics concerns itself with the paths and rates adopted by systems approaching equilibrium
Much of the machinery of thermodynamics can be applied locally under an assumption of local equilibrium.
1.1.1 Classical Thermodynamics and Construction of Kinetic Theories
Thermodynamics grew out of studies of systems that exchange energy
Poincare coined the term thermodynamics to refer to insights that developed out of the first and second laws.
From Gibbs's careful and rigorous derivations of equilibrium conditions of matter, the modern subjects of chemical and material thermodynamics were born
Thermodynamics is precise, but is strictly applicable to phenomena that are unachievable in finite systems in finite amounts of time.
Two fundamental results from classical thermodynamics that form the basis for kinetic theories in materials:
1. If an extensive quantity can be exchanged between two bodies, a condition necessary for equilibrium is that the conjugate potential, which is an intensive quantity, must have the same value throughout both bodies.
There are an infinite number of ways that a potential can differ from its equilibrium value. The task of describing and analyzing nonequilibrium systems is more complex than describing equilibrium systems
2. If a closed system is in equilibrium with reservoirs maintaining constant potentials (e.g. P and T), that system has a free-energy function (e.g., G(P, T) that is minimized at equilibrium. Therefore, a necessary condition for equilibrium is that any variation in G must be nonnegative(dG pt >= 0)