| 1. |
- Charles, Bethan, et al.
(författare)
-
Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites
- 2020
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 32:6, s. 2282-2291
-
Tidskriftsartikel (refereegranskat)abstract
- The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA(+)) of (CH(NH2)(2)PbI3 (FAPbI(3)) and increased resistance to formation of the undesirable.-phase. The structural phase behavior of Cs(0.1)FA(0.9)PbI(3) has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic alpha-phase, Cs(0.1)FA(0.9)PbI(3), is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs(0.1)FA(0.9)PbI(3), a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal beta-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure alpha-FAPbI(3) (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials.
|
|
| 2. |
- Smrcok, Lubomir, et al.
(författare)
-
On hydrogen bonding in 1,6-anhydro-β-D-glucopyranose (levoglucosan): X-ray and neutron diffraction and DFT study
- 2006
-
Ingår i: Acta Crystallographica Section B: Structural Science. - 0108-7681 .- 1600-5740. ; B62:5, s. 912-918
-
Tidskriftsartikel (refereegranskat)abstract
- The geometry of hydrogen bonds in 1,6-anhydro-β-D-glucopyranose (levoglucosan) is accurately determined by refinement of time-of-flight neutron single-crystal diffraction data. Molecules of levoglucosan are held together by a hydrogen-bond array formed by a combination of strong O-H...O and supporting weaker C-H...O bonds. These are fully and accurately detailed by the neutron diffraction study. The strong hydrogen bonds link molecules in finite chains, with hydroxyl O atoms acting as both donors and acceptors of hydroxyl H atoms. A comparison of molecular and solid-state DFT calculations predicts red shifts of O-H and associated blue shifts of C-H stretching frequencies due to the formation of hydrogen bonds in this system.
|
|
| 3. |
- Ting, Valeska P., et al.
(författare)
-
Probing hydrogen positions in hydrous compounds: information from parametric neutron powder diffraction studies
- 2012
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:19, s. 6914-6921
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the extent to which modern detector technology, coupled with a high flux constant wavelength neutron source, can be used to obtain high quality diffraction data from short data collections, allowing the refinement of the full structures (including hydrogen positions) of hydrous compounds from in situ neutron powder diffraction measurements. The in situ thermodiffractometry and controlled humidity studies reported here reveal that important information on the reorientations of structural water molecules with changing conditions can be easily extracted, providing insight into the effects of hydrogen bonding on bulk physical properties. Using crystalline BaCl2 center dot 2H(2)O as an example system, we analyse the structural changes in the compound and its dehydration intermediates with changing temperature and humidity levels to demonstrate the quality of the dynamic structural information on the hydrogen atoms and associated hydrogen bonding that can be obtained without resorting to sample deuteration.
|
|
| 4. |
- Wilson, Chick C., et al.
(författare)
-
Neutron powder diffraction - new opportunities in hydrogen location in molecular and materials structure
- 2014
-
Ingår i: Crystallography Reviews. - 0889-311X. ; 20:3, s. 162-206
-
Forskningsöversikt (refereegranskat)abstract
- The potential of neutron powder diffraction in the location of hydrogen atoms in molecular materials and inorganic-molecular complexes is reviewed. Advances in instrumentation and data collection techniques that have made this field accessible are reviewed, along with a wide range of applications carried out by our collaboration investigating functional materials, hydrogen-containing minerals and molecular compounds. Some of the limitations in this area, particularly for molecular systems, are also addressed.
|
|
| 5. |
- Wilson, Chick C., et al.
(författare)
-
Neutron powder diffraction - new opportunities in hydrogen location in molecular and materials structure
- 2014
-
Ingår i: Crystallography Reviews. - : Informa UK Limited. - 0889-311X .- 1476-3508. ; 20:3, s. 162-206
-
Forskningsöversikt (refereegranskat)abstract
- The potential of neutron powder diffraction in the location of hydrogen atoms in molecular materials and inorganic-molecular complexes is reviewed. Advances in instrumentation and data collection techniques that have made this field accessible are reviewed, along with a wide range of applications carried out by our collaboration investigating functional materials, hydrogen-containing minerals and molecular compounds. Some of the limitations in this area, particularly for molecular systems, are also addressed.
|
|
