function r = equilibrate(self, XY, err, maxsteps, maxiter, loglevel)
% EQUILIBRATE  Set the mixture to a state of chemical equilibrium.
% r = equilibrate(self, XY, err, maxsteps, maxiter, loglevel)
% This method uses a version of the VCS algorithm to find the
% composition that minimizes the total Gibbs free energy of the
% mixture, subject to element conservation constraints. For a
% description of the theory, see Smith and Missen, "Chemical
% Reaction Equilibrium."  The VCS algorithm is implemented in
% Cantera kernel class MultiPhaseEquil.
%
% The VCS algorithm solves for the equilibrium composition for
% specified temperature and pressure. If any other property pair
% other than "TP" is specified, then an outer iteration loop is
% used to adjust T and/or P so that the specified property
% values are obtained. ::
%
%     >> equilibrate(mix, 'TP')
%     >> equilibrate('TP', 1.0e-6, 500)
%
% :param self:
%     Instance of class :mat:func:`Mixture`
% :param XY:
%     Two-letter string specifying the two properties to hold
%     fixed.  Currently, ``'TP'``, ``'HP'``, ``'TV'``, and ``'SP'`` are
%     implemented. Default: ``'TP'``.
% :param err:
%     Error tolerance. Iteration will continue until :math:`\Delta\mu)/RT`
%     is less than this value for each reaction. Default:
%     1.0e-9. Note that this default is very conservative, and good
%     equilibrium solutions may be obtained with larger error
%     tolerances.
% :param maxsteps:
%     Maximum number of steps to take while solving the
%     equilibrium problem for specified T and P. Default: 1000.
% :param maxiter:
%     Maximum number of temperature and/or pressure
%     iterations.  This is only relevant if a property pair other
%     than (T,P) is specified. Default: 200.
% :param loglevel:
%     Set to a value > 0 to write diagnostic output.
%     Larger values generate more detailed information.
% :return:
%     The error in the solution
%

if nargin < 6
    loglevel = 0;
end
if nargin < 5
    maxiter = 200;
end
if nargin < 4
    maxsteps = 1000;
end
if nargin < 3
    err = 1.0e-9;
end
if nargin < 2
    XY = 'TP';
end
r = mixturemethods(31, mix_hndl(self), XY, err, maxsteps, maxiter, loglevel);