text: In general, there are higher order terms present in the free energy, but it is a reasonable approximation to consider the series to fourth order in the order parameter, as long as the order parameter is small. For the system to be thermodynamically stable (that is, the system does not seek an infinite order parameter to minimize the energy), the coefficient of the highest even power of the order parameter must be positive, so . For simplicity, one can assume that , a constant, near the critical temperature. Furthermore, since  changes sign above and below the critical temperature, one can likewise expand , where it is assumed that  for the high-temperature phase while  for the low-temperature phase, for a transition to occur. With these assumptions, minimizing the free energy with respect to the order parameter requires
  The solution to the order parameter that satisfies this condition is either , or
  It is clear that this solution only exists for , otherwise  is the only solution. Indeed,  is the minimum solution for , but the solution  minimizes the free energy for , and thus is a stable phase. Furthermore, the order parameter follows the relation
  below the critical temperature, indicating a critical exponent  for this Landau mean-theory model.
  The free-energy will vary as a function of temperature given by
  From the free energy, one can compute the specific heat,
  which has a finite jump at the critical temperature of size . This finite jump is therefore not associated with a discontinuity that would occur if the system absorbed latent heat, since . It is also noteworthy that the discontinuity in the specific heat is related to the discontinuity in the second derivative of the free energy, which is characteristic of a second-order phase transition. Furthermore, the fact that the specific heat has no divergence or cusp at the critical point indicates its critical exponent for  is .