%

  function J = energy_fun(param,P,psi_data);

  alpha_1 = param(1,1);
  alpha_11 = param(2,1);
  alpha_111 = param(3,1);

  psi = alpha_1*P.^2 + alpha_11*P.^4 + alpha_111*P.^6;
  res = psi - psi_data;
  J = res'*res;