X-ray diffraction high-pressure

Keywords Crystallography High-Pressure X-ray Diffraction Neutron Diffraction... 

Mizukami, S., A. Ohtani, N. Kawai, and E. Ito (1975). High pressure x-ray diffraction studies on p- and a-Mg2SiC>4. Phys. Earth Plan. Ints. 10, 177-82. 

Katrusiak, A. (1990). High pressure X-ray diffraction study on the structure and phase-transition of 1,3-cyclohexanedione crystals. Acta Crystallogr. B, 46,246-56. [239] Katrusiak, A. (1991). High pressure X-ray diffraction studies on organic crystals. Cryst. Res. Tech., 26, 523-31. [239]... 

Katrusiak, A. (1995). High pressure X-ray diffraction of pentaerythritol. Acta Crystallogr. B, 51, 873-9. [239]... 

Figure 1. Schematic of an experimental setnp for high-pressure X-ray diffraction (XRD) experiments on nanocrystals nnder pressure of tens of GPa (1 GigaPascal s 10,000 atmospheres). Nanociystal powder is dissolved in a pressme medinm and placed between two opposing diamonds, which are clear to X-rays and visible absorption. The pressme is applied by bringing the diamond closer together, and measmed nsing pieces of ruby chips placed inside the pressme cell. The XRD diffraction peaks are Debye-Scherrer broadened by the finite size of the particles, yielding information on the shape and size of the nanocrystals before and after the transition, snch as shown in Figure 3.

In recent high-pressure X-ray diffraction, neutron diffraction, and Raman studies on methane hydrate, pressure-induced phase transformations of methane hydrate show that the initial si (MH-sl) successively transforms to the sH (MH-II) at about 0.9 GPa and to the sO (MH-III) at about 2.0 GPa. 

Caution For safety procedures see Appendix 2. Special hardware, software, and experience is usually needed for high-pressure X-ray diffraction. Therefore, anyone interested in this field should first read some of the extensive lit-and preferably contact one of the groups working in this field... 

Katrusiak, A. High-pressure X-ray diffraction studies on organic crystals, Cryst. Res. Techn. 26 (1991) 523-531. 

In a high pressure X-ray diffraction experiment [4] it has been found that the diagram of the cell parameters of the moganite type PON exhibits a change in slope at 8 GPa. This is also an evidence for the occurrence of a phase transformation in the crystal. The pressure of the phase transformations observed in the Raman and in the X-ray experimerimeriments are... 

Fig. 8. Experimental (open symbols) and calculated closed symbols) values of the intrinsic crystal field parameters and of the Sm +-Cl pair in Sm + SrFCl as a function of Sm +-Cl bond length. The experimental bond length was varied with pressure and determined from high pressure X-ray diffraction data. The calculated curve was obtained from an ab initio calculation based on Eq. (33) [210]...

Both Eu and Yb, whose divalent character is an anomaly among the rare earth metals, can be expected to become trivalent at high pressure. Even if the transition pressures are larger by a factor of two than the predicted values, it should be possible to verify its occurrence by a direct high pressure X-ray diffraction study. 

Similar phenomena were observed in AIN the onset of the B3 -> B1 type transformation changes from 20-23 GPa in the bulk material, to 14.5 GPa in nano-crystals and 24.9 GPa in nano-wire samples [179]. Bulk and nanocrystaUine GaN also have been studied by high-pressure X-ray diffraction, revealing the phase transitions from the wurtzite to the NaCl-type phase at 40 GPa for the bulk and 60 GPa for the nanocrystals [180],... 

Jeon S-J, Porter RF, Vohra YK, Ruoff AL (1987) High-pressure X-ray diffraction and optical absorption studies of NH4I to 75 GPa. Phys Rev B 35 4954-4958... 

Mei Q, Sinogeikin S, Shen G et al (2010) High-pressure x-ray diffraction measurements on vitreous Ge02 under hydrostatic conditions. Phys Rev B 81 174113... 

J0rgensen J-E, Jakobsen JM, Jiang JZ et al (2003) High-pressure X-ray diffraction study of bulk- and nanocrystaUine GaN. J Appl Cryst 36 920-925... 

Winzenick M, jayakumar V, Holzapfel WB (1994) High-pressure X-ray diffraction on potassium and mbidium up to 50GPa. Phys Rev B 50 12381-12385 Holzapfel WB (1998) Equations of state for solids under strong compression. High Pressure Res 16 81-126... 

Errandonea, D. Santamaria-Perez, D. Achary, S. N. Tyagi, A. K Gall, P. Gougeon, P. (2011). High-pressure x-ray diffraction study of CdMo04 and EuMo04, J. Appl. Phys. 109, February 2011) 043510-5, ISSN 0021- 8979. 

As a reference, the high-pressure X-ray diffraction measurements of LaAl2 were also performed. The MgCu2 structure is stable up to 30 GPa, and the compression curve shows a smooth change without any anomalies as also seen in Figure 21. This result indicates that the origin of the anomaly in the compression curve of CeAl2 observed aroimd 17 GPa is due to the presence of 4f electrons in the cerium-based compoimd. 

There is however another effect, which could also be responsible for some of the anomalies in tj-r, plots at moderate pressures, where the precise determination of Vq affects the initial tj-values very much. DiflFerent samples of the various actinides may show significant variation in the initial values of Vo, according to their preparation, and this point may have affected the evaluation of high-pressure X-ray diffraction data. 

Isothermal bulk modulus K (GPa) and its pressure derivative Kg for intermetallic compounds of the lanthanides and actinides, as determined from high-pressure X-ray diffraction study. Errors as indicated in the original publications (n.d. not determined.)... 

Isothermal bulk moduli, (GPa), and pressure derivatives Kg determined from high-pressure X-ray diffraction, for the lanthanide (Ln) pnictides and chalcogenides of the B1 structure type. For each compound the table lists, from top to bottom the bulk modulus, in GPa, the pressure derivative, and references. Errors as indicated in the original publications. (x means compound unknown, - studied under pressure, but no compressibility data known, -l- compound exists, but no HPXRD study known and constr. ... 

Pressure-induced structural transitions were observed for monopnictides of La and Ce, for the monochalcogenides of Eu, and for the monotellurides of Ce, Pr, Sm, Eu, and Tm (table 5). Not all of the remaining Ln monopnictides and monochalcogenides have been studied under pressure up to now. Compressibility data derived from high-pressure X-ray diffraction studies are listed in table 6 and plotted versus atomic number in fig. 18. Figure 16 gives an overview over all pressure-induced electronic and structural transitions observed up to now in LnX compounds. 

A large number of B1-type compounds of Th, U, Np and Pu have been investigated by high-pressure X-ray diffraction. Systematic trends in the nature of the high-pressure phases, the transition pressures, the hysteresis to re-transformation on pressure release, and the compressibility were observed for this group of compounds. 

The first attempts to examine californium metal by high-pressure x-ray diffraction, on samples assumed to represent both the trivalent and divalent metal forms, did not provide additional insight into the valence state of the metal the compressibility data obtained from this study were not conclusive [77]. A subsequent study on the dhep (trivalent) form of californium metal found that this structure transformed into an fee structure under pressures of 10-16 GPa... 

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