Recovering local structure information from high‐pressure total scattering experiments. Issue 6 (23rd November 2021)

• Record Type: Journal Article
• Authors: Herlihy, Anna; Geddes, Harry S.; Sosso, Gabriele C.; Bull, Craig L.; Ridley, Christopher J.; Goodwin, Andrew L.; Senn, Mark S.; Funnell, Nicholas P.
• Is Part Of: Journal of applied crystallography. Volume 54:Issue 6(2021)
• Page Start: 1546
• Page End: 1554
• Publication Date: 2021-11-23
• Subjects: total scattering -- high pressure -- neutron diffraction -- pair distribution function; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576721009420
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : A method for subtracting the pairwise correlations of a pressure‐transmitting medium from neutron pair distribution functions obtained under hydrostatic compression is presented and applied to Ni, MgO and α‐quartz. Abstract : High pressure is a powerful thermodynamic tool for exploring the structure and the phase behaviour of the crystalline state, and is now widely used in conventional crystallographic measurements. High‐pressure local structure measurements using neutron diffraction have, thus far, been limited by the presence of a strongly scattering, perdeuterated, pressure‐transmitting medium (PTM), the signal from which contaminates the resulting pair distribution functions (PDFs). Here, a method is reported for subtracting the pairwise correlations of the commonly used 4:1 methanol:ethanol PTM from neutron PDFs obtained under hydrostatic compression. The method applies a molecular‐dynamics‐informed empirical correction and a non‐negative matrix factorization algorithm to recover the PDF of the pure sample. Proof of principle is demonstrated, producing corrected high‐pressure PDFs of simple crystalline materials, Ni and MgO, and benchmarking these against simulated data from the average structure. Finally, the first local structure determination of α‐quartz under hydrostatic pressure is presented, extracting compression behaviour of the real‐space structure.