Speaker
Description
Recent advances in the application of first principles calculations of NMR parameters to periodic systems [1] and the steady increase of computational power, have become attactrove in their use to support experimental measurement. Such calculations often play an important role in the emerging field of NMR crystallography, where NMR spectroscopy is combined with techniques such as diffraction, to aid structure determination [2].
In this talk I will introduce the capabilities of QE-GIPAW [3], which is based on the popular DFT package Quantum Espresso [4]. After reviewing the underlying theory of the magnetic response of periodic systems, I will highlight how QE and QE-GIPAW can be used in a computational workflow, integrated with NMR/EPR simulation software like Simpson [5] and EasySpin [6]. I will present two case studies of the structure determination of purely inorganic and pharmaceutical crystal polymorphs, where the QE-GIPAW provided a correct assignement of the 1H and 13C NMR shifts.
Finally, I will briefly illustrate the plans to provide a user friendly cif-to-spectrum workflow to be run in the cloud or on premises, thus avoiding the complication of installing and compiling the complete software stack.
[1] C. J. Pickard and F. Mauri, All-electron magnetic response with pseudopotentials: NMR chemical shifts, Phys. Rev. B 63, 245101 (2001); J. R. Yates, C. J. Pickard and F. Mauri, Calculation of NMR chemical shifts for extended systems using ultrasoft pseudopotentials, Phys. Rev. B 76, 024401 (2007)
[2] S. E. Ashbrook and D. McKay, Combining solid-state NMR spectroscopy with first-principles calculations – a guide to NMR crystallography, Chem. Commun. 52, 7186 (2016); D. L. Bryce, NMR crystallography: structure and properties of materials from solid-state nuclear magnetic resonance observables, IUCrJ 4, 350 (2017)
[3] N. Varini, D. Ceresoli, L. Martin-Samos, I. Girotto and C. Cavazzoni, Enhancement of DFT-calculations at petascale: Nuclear Magnetic Resonance, Hybrid Density Functional Theory and Car–Parrinello calculations, Comp. Phys. Commun. 184, 1827 (2013); https://github.com/dceresoli/qe-gipaw
[4] P. Giannozzi et al., QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials, J. Phys.; Cond. Mat. 21, 395502 (2009)
[5] M. Bak, J. T. Rasmussen and N. C. Nielsen, SIMPSON: A General Simulation Program for Solid-State NMR Spectroscopy, J. Magn. Res. 147, 296 (2000)
[6] S. Stoll and A. Schweiger, EasySpin, a comprehensive software package for spectral simulation and analysis in EPR, J. Magn. Res. 178, 42 (2006)
