def write_bulk_modulus_temperature(self, filename="bulk_modulus-temperature.dat"):
        """Write bulk modulus vs temperature in file."""
        w = open(filename, "w")
        for i in range(self._len):
            w.write(
                "%20.15f %25.15f\n"
                % (self._temperatures[i], self._equiv_bulk_modulus[i])
            )
        w.close()