However, the approach taken in this paper (examining the full set of dispersion curves) was not followed in [@Wang_Y2Mo3O12; @Romao_Y2Mo3O12].

Methodology
===========

*Ab-initio* calculations
------------------------

  ------------------ -------- -------- -------- -------- -------- --------
        Space group:                                              
    Cell parameters:                                              
                                                                  
                                                                  
                       $x$      $y$      $z$      $x$      $y$      $z$
                   Y  0.4697   0.3833   0.2496   0.4669   0.3813   0.2493
                   W  0.2500   0.0000   0.4731   0.2500   0.0000   0.4739
                   W  0.1112   0.3574   0.3884   0.1167   0.3562   0.3928
                   O  0.0839   0.1396   0.0615   0.0905   0.1395   0.0675
                   O  0.1402   0.0644   0.3719   0.1343   0.0614   0.3723
                   O  0.0217   0.2629   0.3175   0.0177   0.2657   0.3211
                   O  0.3387   0.4209   0.0749   0.3332   0.4155   0.0767
                   O  0.0583   0.4648   0.3179   0.0732   0.4690   0.3226
                   O  0.2812   0.3435   0.3563   0.2868   0.3340   0.3613
                                                                  
                 W–O                                              
                 Y–O                                              
                 W–Y                                              
  ------------------ -------- -------- -------- -------- -------- --------

  : Structural data for the Y$_2$W$_3$O$_{12}$ equilibrium cell, as optimised at 0 GPa via DFT in CASTEP. Experimental data obtained for Y$_2$W$_3$O$_{12}$ from neutron diffraction at 0 GPa and 15 K [@Forster_Sleight_1999_IntJInorgMat_Y2W3O12NTEExpt] are given alongside for comparison. The *ab-initio* results are very close to the experimentally-derived values.

\[Y2W3O12EquilibriumCell\]

Density Functional Theory (DFT) calculations were carried out using the CASTEP code [@Clark_etal_2005_ZKrist_CASTEP]. This uses a plane-wave basis set to describe the electronic wave functions together with the pseudopotential method to remove the need to handle core 