In what follows, we focus our discussion and theoretical analysis on the combination of HCN with 15 ethane. Ethane has a low conformational flexibility, which limits computational costs. Ethane is also less experimentally challenging to handle compared to methane, which additionally acts as a free rotor inside materials and effectively invalidates the quasi-20 harmonic approximation we rely on in computational vibrational analysis. a Raman intensity: s = strong, m = medium, w = weak. b feature is smooth, see Fig. . c Data for predicted lowest energy structures illustrated in Fig. . Table provides data for additional near-energy structures.