Nearest-neighbour distribution of distances in crystals from extended X-ray absorption fine structure

Fornasini, P.; Grisenti, R.; Dapiaggi, Monica; Agostini, Giovanni; Miyanaga, Takafumi

doi:10.1063/1.4995435

Cited by 31 publications

(46 citation statements)

References 101 publications

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“…The asymmetry parameter C 3 , which also increases with increasing temperature, was described using the corresponding Einstein model expression with terms to third order [31], yielding values up to 10 −4Å 3 at room temperature in good agreement with previous work [33,35]. All higher cumulants were set to zero because a full anharmonic fit using the fourth-order terms up to the fourth cumulant [36] showed no significant difference of the resulting bond-stretching force constants but strongly reduced the stability of the fit.…”

Section: Discussionsupporting

confidence: 87%

Bond-strength inversion in (In,Ga)As semiconductor alloys

et al. 2018

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The atomic-scale structure and vibrational properties of semiconductor alloys are determined by the energy required for stretching and bending the individual bonds. Using temperature-dependent extended x-ray absorption fine-structure spectroscopy, we have determined the element-specific In-As and Ga-As effective bond-stretching force constants in (In,Ga)As as a function of the alloy composition. The results reveal a striking inversion of the bond strength where the originally stiffer bond in the parent materials becomes the softer bond in the alloy and vice versa. Our findings clearly demonstrate that changes of both the individual bond length and the surrounding matrix affect the bond-stretching force constants. We thus show that the previously used common assumptions about the element-specific force constants in semiconductor alloys do not reproduce the composition dependence determined experimentally for (In,Ga)As.

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Section: Discussionsupporting

confidence: 87%

Bond-strength inversion in (In,Ga)As semiconductor alloys

et al. 2018

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“…As a consequence, the reduction of the bond distance is progressively smaller than the reduction of the crystallographic distance (proportional to the lattice parameters), so that the bond compressibility becomes progressively smaller than the lattice compressibility. The complex relationships between force constants, cumulants and asymmetry parameter is discussed on general grounds in [9]. We suggest here that the slight increase of asymmetry when the pressure increases can be somewhat connected to the perpendicular vibrations and in particular to the increase of vibrational anisotropy (to be further discussed in Section 5.2.2), which would progressively enhance the contribution of the larger distances to the distribution.…”

Section: Bond and Lattice Compressibilitiesmentioning

confidence: 72%

“…The effective pair potential is in principle dependent on temperature and pressure. In constant-pressure measurements as a function of temperature, the effective force constants k i can be generally considered as independent of temperature [39]; a rigid shift of the effective potential has anyway to be taken into account, which significantly contributes to the bond expansion measured by the first cumulant [9].…”

Section: Bond and Lattice Compressibilitiesmentioning

confidence: 99%

Bond compressibility and bond Grüneisen parameters of CdTe

Fornasini¹,

Grisenti²,

Irifune³

et al. 2018

J. Phys.: Condens. Matter

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Extended x-ray absorption fine structure (EXAFS) at the Cd K edge and diffraction patterns have been measured on CdTe as a function of pressure from 100 kPa (1 bar) to 5 GPa using a cell with nano-polycrystalline diamond anvils and an x-ray focussing scanning spectrometer. Three phases-zincblende (ZB), mixed cinnabar-ZB and rocksalt (RS)-are well distinguished in different pressure intervals. The bond compressibility measured by EXAFS in the ZB phase is slightly smaller than the one measured by diffraction and decreases significantly faster when the pressure increases; the difference is attributed to the effect of relative vibrations perpendicular to the Cd-Te bond. The parallel mean square relative displacement (MSRD) decreases, the perpendicular MSRD increases when the pressure increases, leading to an increasing anisotropy of relative atomic vibrations. A constant-temperature bond Grüneisen parameter (GP) has been evaluated for the ZB phase and compared with the constant-pressure bond GP measured in a previous experiment; an attempt is made to connect the bond GPs measured by EXAFS and the more familiar thermodynamic GP and mode GPs; the comparisons suggest the inadequacy of the quasi-harmonic approximation to deal with the local vibrational properties sampled by EXAFS.

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“…Mechanism (iv) involves some change in symmetry or space group of a crystal [28][29][30]. As to the mechanism (v), earlier, Barron et al [1,15,20,22,[31][32][33] argued qualitatively that the tension effect is responsible for the NTE in ZB and diamond semiconductors. Upon heating, transverse motion causes the bond to shorten and decreases volume in solids.…”

Section: Introductionmentioning

confidence: 99%

A systematic study of the negative thermal expansion in zinc-blende and diamond-like semiconductors

et al. 2019

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Upon heating, almost all zinc-blende (ZB) and diamond-like semiconductors undergo volume contraction at low temperature, i.e. negative thermal expansion (NTE), instead of commonly expected expansion. Specifically, CuCl has the largest NTE among these semiconductors with a coefficient comparable with the record value of ZrW 2 O 8 . So far, underlying physical mechanism remains ambiguous. Here, we present a systematic and quantitative study of the NTE in ZB and diamond-like semiconductors using first-principles calculations. We clarified that the material ionicity, which renders the softening of the bond-angle-bending and thus, the enhancement of excitation of the transverse acoustic (TA) phonon, is responsible for the NTE of ZB and diamond-like semiconductors. With the increase in the ionicity from the groups IV, III-V, IIB-VI to IB-VII ZB semiconductors, the coefficient of the maximum NTE increases due to the weakness in bond-rotation effect, which makes the relative motion between cation and anion transverse to the direction of the bond more feasible and the mode Grüneisen parameters of the TA modes more negative. Since CuCl has the highest ionicity among all ZB and diamond-like semiconductors, it is expected to have the largest NTE, in good agreement with the experimental observation. This understanding would be beneficial for tetrahedral materials with specific applications.

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Nearest-neighbour distribution of distances in crystals from extended X-ray absorption fine structure

Cited by 31 publications

References 101 publications

Bond-strength inversion in (In,Ga)As semiconductor alloys

Bond-strength inversion in (In,Ga)As semiconductor alloys

Bond compressibility and bond Grüneisen parameters of CdTe

A systematic study of the negative thermal expansion in zinc-blende and diamond-like semiconductors

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