Resolution enhancement of 1 H NMR shifts in K‐struvite and newberyite via partial deuteration

Abstract We present a magic‐angle spinning nuclear magnetic resonance (MAS NMR) study of K‐struvite (MgKPO 4 ·6H 2 O) and newberyite (MgHPO 4 ·3H 2 O), two phosphate compounds that are found in hydrated magnesium potassium phosphate (MKP) cements, which are currently receiving a special care in literature as environmental sustainable construction materials. We show that an unprecedented resolution of 1 H MAS NMR spectra is achieved via synthesis of deuterated samples using D 2 O, in contrast to poorly resolved spectra obtained in protonated samples. The level of deuteration can be estimated from thermogravimetric analysis measurements and found to be around 80%. Using a set of magnesium phosphate compounds with a known structure and NMR data, density functional theory (DFT) gauge including projector augmented waves (GIPAW) calculations of 1 H, 2 H, and 31 P NMR parameters are predicted using DFT‐optimized structures. 31 P predicted NMR shift values are found to be in excellent agreement with experimental values. For 1 H, we observe discrepancies for newberyite, suggesting that important dynamical effects (such as water molecule vibrations) are at work at room temperature, in contrast to K‐struvite. This hypothesis is supported by a detailed comparison of NMR observables such as nuclear relaxation times T 1 . This work opens appealing perspectives for improving NMR studies of MKP cement‐based materials via 1 H NMR and synthesis of deuterated samples.