<p>Atoms in every solid are tied up with chemical bonds and are vibrating constantly with thermal energy, even when the material appears perfectly still. These chemical bonds and atomic arrangements are the primary deciding factors for the observed physical properties of the materials. The collective quantized vibrations of atoms are called <i>phonons, and</i> they play a central role in how electrons move, how light interacts with materials, and how heat transfers through the solids. Inorganic halides are promising materials to understand the modified physical properties arising because of dynamics of the atomic arrangements and anharmonicity of the chemical bonds. Di-thallium silver tri-iodide (Tl₂AgI₃) is one such example of solid with zero-dimensional clusters showcasing a new region of wave like (non-diffusive) heat transport, breaking the conventional understanding of particle like thermal propagation. Understanding this new mechanism is important for the development of technologies ranging from thermoelectric energy conversion to thermal managements in micro-nano-electronics and quantum devices.</p> Graphical abstract <p></p>