THE MODEL-FREE QUEST FOR DISORDERED PROTONS IN SOLIDS

It is commonplace to assert that neutrons are a good probe for protons and deuterons in solids, all the more so when all the remaining atoms (backbone) are reasonably well known from previous accurate X-ray mea surements. When the protons are disordered, however, good is not good enough without a suitable unconventional das analysis. By (i) removing most of the truncation effects, (ii) allowing for the use of prior ch emical knowledge, (iii) making use of the experimental error bars and (iv) taking advantage of the negative scattering length of the proton which overrides the huge incoherent cross-section of the latter (at le ast in the case of single-crystal diffraction), maximum entropy assert s itself as an ideal tool for model-free computer-assisted proton visi on that easily supersedes the commonly used Fourier and difference Fou rier syntheses. A typical example will be discussed.