In the papers about first principles (or ab initio) calculations, there are three energies which are often calculated: "binding energy", "cohesive energy" and "formation energy". Their meanings are alike, therefore they confuse me a lot. Can someone konw the correct definitions of them and show their differences in tail?
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1 Answer
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Typically:
Formation energy is the change in energy when a material is formed from it's constituent elements in their reference states. For example, the formation energy of alumina (Al2O3) is the change in energy when fcc aluminum and O2 gas combine to make Al2O3.
Cohesive energy is the amount of energy it takes to break something up into isolated atoms. This is also called the atomization energy.
Binding energy in general means the amount of energy to split something up, and can mean different things depending on the context. For example, if you're talking about a molecule, it can refer to atomization energy.
Something to keep in mind regarding sign conventions is that formation energies are typically given as negative values, whereas cohesive energies and binding energies are typically positive values.
