pair distribution function
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2022 ◽  
Author(s):  
Samantha E. Russell ◽  
Susan E. Henkelis ◽  
Simon M. Vornholt ◽  
Daniel N. Rainer ◽  
Karena W. Chapman ◽  
...  

Correction for ‘In situ flow pair distribution function analysis to probe the assembly–disassembly–organisation–reassembly (ADOR) mechanism of zeolite IPC-2 synthesis’ by Samantha E. Russell et al., Mater. Adv., 2021, DOI: 10.1039/d1ma00335f.


Author(s):  
Jonas Beyer ◽  
Nikolaj Roth ◽  
Bo Brummerstedt Iversen

Powder diffraction and pair distribution function (PDF) analysis are well established techniques for investigation of atomic configurations in crystalline materials, and the two are related by a Fourier transformation. In diffraction experiments, structural information, such as crystallite size and microstrain, is contained within the peak profile function of the diffraction peaks. However, the effects of the PXRD (powder X-ray diffraction) peak profile function on the PDF are not fully understood. Here, all the effects from a Voigt diffraction peak profile are solved analytically, and verified experimentally through a high-quality X-ray total scattering measurement on Ni powder. The Lorentzian contribution to the microstrain broadening is found to result in Voigt-shaped PDF peaks. Furthermore, it is demonstrated that an improper description of the Voigt shape during model refinement leads to overestimation of the atomic displacement parameter.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
G. I. González-Pedreros ◽  
J. A. Camargo-Martínez ◽  
F. Mesa

AbstractCooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$ N cp parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$ T c . Herein, we reported $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) function of the compressed $$D_3S$$ D 3 S and $$H_3S$$ H 3 S high-$$T_c$$ T c conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$ H 3 S . $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$ H 3 S by its stable isotopes can lead to important changes in $$T_c$$ T c . The results also show proportionality between $$N_{cp}$$ N cp parameter and experimental or theoretical $$T_c$$ T c values.


Author(s):  
Gianpiero Gallo ◽  
Maxwell W. Terban ◽  
Igor Moudrakovski ◽  
Tatjana Huber ◽  
Martin Etter ◽  
...  

A new six-membered cyclic alkanolamine with chemical formula C6H15N3O3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1H/13C/15N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit-cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior.


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