lecture3

Statistical Thermodynamics

Based on the definitions of internal energy and entropy,

we can derive the remaining thermodynamic functions in terms of the canonical partition function, Q.

The Helmholtz free energy is A = U – TS, therefore

The pressure can be calculated from

which is the same as:

From the combination of U and P we obtain

H = U + PV

From the combination of A and P we obtain

G = A + PV

For indistinguishable particles

q_m is a molar partition function q_m = q/n.

For distinguishable particles:

and

where q is a molecular partition function.

The molecular partition function, q = q^Tq^Rq^Vq^E factorizes into partition functions for translation, q^T, rotation, q^R, vibration, q^V, and electronic states, q^E.