== MS_build_isotropic

 MS_BUILD_ISOTROPIC - Create elasticity matrix from pairs of isotropic moduli.

 // Part of MSAT - The Matlab Seismic Anisotropy Toolkit //

 Given two isotropic moduli create an elasticity matrix for an isotropic 
     material and optionally return all other moduli.

  [C, ...]=MS_build_isotropic('modname1', mod1, 'modname2', mod2')

 Usage: 
     [C]=MS_build_isotropic('modname1', mod1, 'modname2', mod2')                    
          Given two isotropic moduli mod1 and mod2 named as strings 
          'modname1' and 'modname2' return an elasticity matrix C.
          Permitted moduli are:
              'lam' - first lame parameter, in GPa
              'mu' - shear modulus (second Lame parameter), in GPa
              'K' - bulk modulus, in GPa.
              'E' - Young's modulus, in GPa.
              'nu' - Poisson's ratio, dimensionless.
              'M' - 'P-wave modulus', in GPa.

     [C, K, E, lam, mu, nu, M]=MS_build_isotropic('modname1', mod1, 'modname2', mod2') 
          Also return all 6 moduli.

 Notes:
     Not all combinations of moduli are valid / implemented

 References:
     Stacey F. D. and Davis, P. M. (2008) Physics of the Earth 4th ed. 
     Appendix D and Section 10.2.

 See also: MS_POLYAVERAGE
