Returns the percentage volume change.

        Returns:
            Volume change in percentage, e.g., 0.055 implies a 5.5% increase.

def get_percentage_volume_change(self):
        """
        Returns the percentage volume change.

        Returns:
            Volume change in percentage, e.g., 0.055 implies a 5.5% increase.
        """
        initial_vol = self.initial.lattice.volume
        final_vol = self.final.lattice.volume
        return final_vol / initial_vol - 1