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The crystal structure of the ternary germanide Li2MnGe has been re‐evaluated from single‐crystal X‐ray diffraction data. This compound crystallizes in a non‐centrosymmetric superstructure of the ZrCuSiAs type (space groupP4bm, Pearson codetP16), with the lattice parametersa= 6.088(4) Å,c= 6.323(4) Å. First‐principle calculations for the idealized structure predict antiferromagnetic exchange in the square Mn nets and semimetallic ground state. In addition, a new ternary phase with the composition Li2–xMn4+xGe5(x≈ 1.2) was discovered. It adopts the V6Si5structure type (space groupIbam, Pearson codeoI44), with the lattice parametersa= 7.570(2) Å,b= 16.323(3) Å,c= 5.057(1) Å. DSC/TG measurements show that this compound is thermally stable below 995 K.
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On the Origin and Structure of the First Sharp Diffraction Peak of Amorphous Silicon
The structure of the first sharp diffraction peak (FSDP) of amorphous silicon (a‐Si) near 2 Å−1is addressed with particular emphasis on the position, intensity, and width of the diffraction curve. By studying a number of continuous random network (CRN) models of a‐Si, it is shown that the position and intensity of the FSDP are primarily determined by radial atomic correlations in the amorphous network on the length scale of 15 Å. A shell‐by‐shell analysis of the contribution from different radial shells reveals that key contributions to the FSDP originate from the second and fourth radial shells in the network, which are accompanied by a background contribution from the first shell and small residual corrections from the distant radial shells. The results from numerical calculations are complemented by a phenomenological discussion of the relationship between the peaks in the structure factor in the wavevector space and the reduced pair‐correlation function in the real space. An approximate functional relation between the position of the FSDP and the average radial distance of Si atoms in the second radial shell in the network is derived, which is corroborated by numerical calculations.
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- Award ID(s):
- 1833035
- PAR ID:
- 10239930
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- physica status solidi (b)
- Volume:
- 258
- Issue:
- 9
- ISSN:
- 0370-1972
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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