$indexed single crystal diffraction pattern bcc$

$indexed single crystal diffraction pattern bcc$

#Indexed single crystal diffraction pattern bcc full#

Seven samples were tested with 300 μm culets anvils and three samples were tested with 200 μm culet anvils. No bridging was observed after loading to pressures as high as 58 ± 2 GPa except of partial bridging of one sample illustrated in the supplementary material of the paper. After loading to the highest pressure, samples were investigated by optical or electron microscopy to determine presence of bridging (squishing) samples between diamonds. Rhenium (Re) gasket was pre-indented down to 35 μm and a hole of 150 or 100 μm diameter was drilled in the gasket for 300 and 200 um culets respectively. The smaller culet allows achieving higher pressure but causes higher stress gradient 15, 16, 17. DACs with culets 300 and 200 μm in diameter were used for different samples. For detailed description and illustration of DAC reader is referred to 14. All samples were loaded in DAC in a way that basal plane of HCP crystal is perpendicular to the X-ray beam and parallel to the DAC plane. Each sample was put into a diamond anvil cell (DAC) BX90 using a micromanipulator 12. Specimens of pure Mg with nominal purity 99.9 + % were cut from a bulk Mg single crystal into small pieces with a thickness of ~ 10 um using a laser drilling machine at HPCAT 13.

#Indexed single crystal diffraction pattern bcc full#

Upon the full transformation, a powder-like BCC aggregate is formed revealing the destructive nature of the HCP to BCC transformation in single crystals of Mg. The peak intensity increases at 59.7 GPa. Nevertheless, the powder diffraction shows the formation of 110 BCC peak at 56.6 GPa. Intensity of the Laue reflections from HCP crystals rapidly decrease but no reflections from crystalline BCC phase are observed with a further increase of pressure. The selected crystals are tracked by mapping Laue diffraction spots up to the onset of the HCP to BCC transformation, which is determined to be at a pressure of 56.6 ± 2 GPa. The plasticity is accommodated by dislocation glide causing local misorientations of up to 1°–2°. Although experiments were performed with both He and Ne pressure media, crystals inevitably undergo plastic deformation upon loading to 40–44 GPa. The conclusion, I suppose, is thus that whenever we see Miller indices used to describe planes in fcc or bcc, by convention these are not in fact coordinates in the corresponding reciprocal lattices bcc and fcc, respectively (as they would be by the strict definition of Miller indices), but are instead coordinate in the reciprocal simple cubic lattice (to the underlying simple cubic direct lattice used to describe the crystal)? I can accept this only if the one-to-one correspondence asked about above exists.Mechanisms of hexagonal close-packed (HCP) to body-centered cubic (BCC) phase transformation in Mg single crystals are observed using a combination of polychromatic beam Laue diffraction and monochromatic beam powder diffraction techniques under quasi-hydrostatic pressures of up to 58 ± 2 GPa at ambient temperature. In practice, it is only in the description of noncubic crystals that one must remember that the Miller indices are the coordinates of the normal in a system given by the reciprocal lattice, rather than the direct lattice. Also, does the converse hold? Is every lattice plane in the underlying simple cubic lattice also a lattice plane in the given fcc or bcc structure? Essentially, I am asking for a proof that, given a fixed bcc or fcc lattice, there is a one-to-one correspondence between lattice planes as described in bcc or fcc and as described in the underlying simple cubic lattice. It is the bolded part which I am asking about - I can convince myself intuitively that this should be true, but cannot prove it. Since any lattice plane in a fcc or bcc lattice is also a lattice plane in the underlying simple cubic lattice, the same elementary cubic indexing can be used to specify lattice planes. Ashcroft and Mermin remark, at the bottom of page 91 thatĪs a general rule, face-centered and body-centered cubic Bravais lattice are described in terms of a conventional cubic cell, i.e.

$indexed single crystal diffraction pattern bcc$