In thermodynamics, Gibbs free energy, involving entropy, can characterize spontaneous processes. Can something similar be achieved concerning atomic and nuclear processes by means of the notion of von Neumann entropy?
No. Entropy simply counts states, it doesn't imply anything about the transition rates between states.
The free energy simply implies that, at finite temperature, the energy of a state isn't enough to describe how likely it is for the system to be found in it, the number of states that are available, thanks to the interaction with the bath, is needed.
hi, Stam Nicolis - thanks for your answer - BUT: Gibbs free energy is/must be negative for spontaneous processes - which are TRANSITIONS
though you are right: this is not about transition RATES
anyway, my question was whether von Neumann entropy can function in a similar way - characterizing a transition as spontaneous (without indicating any rate)
(and sorry for the misprint ‘non’) greetings ppk
Hello! Why not? Suppose that an atom is in an excited state in a vacuum, it can be described by a wave function, and this is a pure state, the entropy for it is zero. After spontaneous emission of a photon, we get a mixture that includes two states. There is one atom in the ground state and one photon. I believe that the entropy of such a system will increase.
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