Ising Model — Transfer Matrix Exact Solution

Onsager (1944): exact free energy of the 2D Ising model
Temperature T/Jk 2.27
Field h/J 0.00
Grid Size 40
MC Steps/Frame 1000
Onsager's 1944 exact solution: F/N = -kT[ln(2cosh(2K)) + (1/2π)∫₀^π ln(√(cosh²(2K)² - sinh(2K)·cos(θ)))dθ], where K=J/kT. Critical temperature: Tc = 2J/ln(1+√2) ≈ 2.269J/k. Order parameter ⟨m⟩ = (1-sinh(2K)⁻⁴)^(1/8) for T