e,
                        fractional_masses=None,
                        thickness=None,
                        density=None):
        &#34;&#34;&#34;
        Create a new material given the composition and fractional masses.

        Parameters
        ----------
        name : `str`
            Name of the meterial
        fractional_masses : `dict`
            The element and fractional masses of the material e.g. `{&#39;H&#39;: 0.031, &#39;O&#39;: 0.969}`
        thickness : `astropy.units.Quantity`
