2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/164550We show with neutron diffraction that a single-crystal of potassium hydrogen deuterium carbonate at room temperature, namely KH$_{0.76}$D$_{0.24}$CO$_3$, is isomorphous with the KHCO$_3$ and KDCO$_3$ derivatives. Protons and deuterons are not disordered particles located at definite sites and Bragg peaks are best fitted with separate H and D sublattices. We propose a theoretical framework for nonlocal observables and macroscopic states compatible with the crystal field.Other Condensed MatterQuantum Physicstext