def plot_pdf_gibbs_temperature(self, filename="gibbs-temperature.pdf"):
        """Plot Gibbs free energy vs temperature in pdf."""
        import matplotlib.pyplot as plt

        self._set_rcParams(plt)

        fig, ax = plt.subplots()
        ax.xaxis.set_ticks_position("both")
        ax.yaxis.set_ticks_position("both")
        ax.xaxis.set_tick_params(which="both", direction="in")
        ax.yaxis.set_tick_params(which="both", direction="in")

        self._plot_gibbs_temperature(ax)
        plt.savefig(filename)
        plt.close()