Sergey Mitryukovskiy, Danny E. P. Vanpoucke, Yue Bai, Théo Hannotte, Mélanie Lavancier, Djamila Hourlier, Goedele Roos, Romain Peretti, Vanpoucke, Danny/0000-0001-5919-7336, Mitryukovskiy, Sergey, VANPOUCKE, Danny E.P., Bai, Yue, Hannotte, Theo, Lavancier, Melanie, Hourlier, Djamila, Roos, Goedele, Peretti, Romain, Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA), Université catholique de Lille (UCL)-Université catholique de Lille (UCL), Hasselt University (UHasselt), Maastricht University [Maastricht], Photonique THz - IEMN (PHOTONIQUE THZ - IEMN), Université catholique de Lille (UCL)-Université catholique de Lille (UCL)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA), EPItaxie et PHYsique des hétérostructures - IEMN (EPIPHY - IEMN), Unité de Glycobiologie Structurale et Fonctionnelle - UMR 8576 (UGSF), Université de Lille-Centre National de la Recherche Scientifique (CNRS), This work was partially supported by: i) the international chair of excellence 'ThOTroV' from region 'Hauts-de-France', ii) the welcome talent grant 'NeFiStoV' fromEuropean metropole of Lille, iii) the 'TeraStoVe' grant from I-site ULNE, iv) the French government through the National Research Agency (ANR) under program PIA EQUIPEXLEAF ANR-11-EQPX-0025 and ExCELSiOR ANR 11-EQPX-0015, and v) the French RENATECH network on micro and nanotechnologies. The computational resources and services used in this work were provided by the Centre de Ressources Informatiques (CRI) and by the VSC (Flemisch Supercomputer Center), funded by the Research Foundation Flanders (FWO) and the Flemisch Government – department EWI., Renatech Network, ANR-11-EQPX-0025,LEAF,Plateforme de traitement laser pour l'électronique flexible multifonctionnelle(2011), ANR-11-EQPX-0015,Excelsior,Centre expérimental pour l'étude des propriétés des nanodispositifs dans un large spectre du DC au moyen Infra-rouge.(2011), Université de Lille, CNRS, Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 [IEMN], Hasselt University [UHasselt], Institut d'Électronique, de Microélectronique et de Nanotechnologie (IEMN) - UMR 8520, and Unité de Glycobiologie Structurale et Fonctionnelle (UGSF) - UMR 8576
The nanoscale structure of molecular assemblies plays a major role in many (mu)-biological mechanisms. Molecular crystals are one of the most simple of these assemblies and are widely used in a variety of applications from pharmaceuticals and agrochemicals, to nutraceuticals and cosmetics. The collective vibrations in such molecular crystals can be probed using terahertz spectroscopy, providing unique characteristic spectral fingerprints. However, the association of the spectral features to the crystal conformation, crystal phase and its environment is a difficult task. We present a combined computational-experimental study on the incorporation of water in lactose molecular crystals, and show how simulations can be used to associate spectral features in the THz region to crystal conformations and phases. Using periodic DFT simulations of lactose molecular crystals, the role of water in the observed lactose THz spectrum is clarified, presenting both direct and indirect contributions. A specific experimental setup is built to allow the controlled heating and corresponding dehydration of the sample, providing the monitoring of the crystal phase transformation dynamics. Besides the observation that lactose phases and phase transformation appear to be more complex than previously thought - including several crystal forms in a single phase and a non-negligible water content in the so-called anhydrous phase - we draw two main conclusions from this study. Firstly, THz modes are spread over more than one molecule and require periodic computation rather than a gas-phase one. Secondly, hydration water does not only play a perturbative role but also participates in the facilitation of the THz vibrations. We thank the referees for their review – it has allowed us to improve the manuscript, and especially the excellent suggestion to check our findings by X-ray diffraction. We thank Dr Florent Blanchard and Dr Pascal Roussel for their kind help with that experiment. This work was partially supported by: (i) the international chair of excellence ‘‘ThOTroV’’ from region ‘‘Hauts-de- France’’; (ii) the welcome talent grant ‘‘NeFiStoV’’ from European metropole of Lille; (iii) the ‘‘TeraStoVe’’ grant from I-site ULNE; (iv) the French government through the National Research Agency (ANR) under program PIA EQUIPEX LEAF ANR-11-EQPX-0025 and ExCELSiOR ANR 11-EQPX-0015; and (v) the French RENATECH network on micro and nanotechnologies. The computational resources and services used in this work were provided by the Centre de Ressources Informatiques (CRI) and by the VSC (Flemisch Supercomputer Center), funded by the Research Foundation Flanders (FWO) and the Flemisch Government – department EWI.