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On the question of commensurability - The Nowotny chimney-ladder structures revisited

Rohrer, F. E. ; Lind, H. ; Eriksson, L. ; Larsson, A. K. and Lidin, S. LU (2000) In Zeitschrift fur Kristallographie 215(11). p.650-660
Abstract

A composite approach was used for the structure solution and refinement of two new Nowotny chimney-ladder phases, (Mo/Rh)11Ge18 and (Mo/Rh)13Ge22, found during investigations in the Mo/Rh/Ge system. The descriptions of the phases with conventional models (in I4̄2d (No. 122) with a = 5.885(2) Å, c = 52.62(2) Å for (Mo/Rh)11Ge18 and a = 5.922(1) Å, c = 62.88(4) Å for (Mo/Rh)13Ge22) led to high numbers of unobserved reflections, high parameter/reflection ratios and an unstable refinement in the case of (Mo/Rh)13Ge22. Microscopy studies showed that the phases were in fact incommensurately modulated. Therefore, a composite model... (More)

A composite approach was used for the structure solution and refinement of two new Nowotny chimney-ladder phases, (Mo/Rh)11Ge18 and (Mo/Rh)13Ge22, found during investigations in the Mo/Rh/Ge system. The descriptions of the phases with conventional models (in I4̄2d (No. 122) with a = 5.885(2) Å, c = 52.62(2) Å for (Mo/Rh)11Ge18 and a = 5.922(1) Å, c = 62.88(4) Å for (Mo/Rh)13Ge22) led to high numbers of unobserved reflections, high parameter/reflection ratios and an unstable refinement in the case of (Mo/Rh)13Ge22. Microscopy studies showed that the phases were in fact incommensurately modulated. Therefore, a composite model consisting of a rather stable diamond-like transition-metal substructure and a helical main-group-metal arrangement was developed. For the refinement of both phases, (Mo/Rh)11Ge18 as well as (Mo/Rh)13Ge22, the same model - same space group pair (W : P4/nnc : q1̄q1 P : I41/amd : 11̄ss), same atom positions and modulation waves - was used. The refinements converged rapidly, showing that the presented structure model is very general, and may well be applicable to any Nowotny chimney-ladder phase.

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author
; ; ; and
publishing date
type
Contribution to journal
publication status
published
in
Zeitschrift fur Kristallographie
volume
215
issue
11
pages
11 pages
publisher
Oldenbourg Verlag
external identifiers
  • scopus:0033709365
ISSN
0044-2968
DOI
10.1524/zkri.2000.215.11.650
language
English
LU publication?
no
id
3a72d5f4-7f8c-4345-9f02-7898e761c7c2
date added to LUP
2019-04-08 16:01:36
date last changed
2022-01-31 18:52:00
@article{3a72d5f4-7f8c-4345-9f02-7898e761c7c2,
  abstract     = {{<p>A composite approach was used for the structure solution and refinement of two new Nowotny chimney-ladder phases, (Mo/Rh)<sub>11</sub>Ge<sub>18</sub> and (Mo/Rh)<sub>13</sub>Ge<sub>22</sub>, found during investigations in the Mo/Rh/Ge system. The descriptions of the phases with conventional models (in I4̄2d (No. 122) with a = 5.885(2) Å, c = 52.62(2) Å for (Mo/Rh)<sub>11</sub>Ge<sub>18</sub> and a = 5.922(1) Å, c = 62.88(4) Å for (Mo/Rh)<sub>13</sub>Ge<sub>22</sub>) led to high numbers of unobserved reflections, high parameter/reflection ratios and an unstable refinement in the case of (Mo/Rh)<sub>13</sub>Ge<sub>22</sub>. Microscopy studies showed that the phases were in fact incommensurately modulated. Therefore, a composite model consisting of a rather stable diamond-like transition-metal substructure and a helical main-group-metal arrangement was developed. For the refinement of both phases, (Mo/Rh)<sub>11</sub>Ge<sub>18</sub> as well as (Mo/Rh)<sub>13</sub>Ge<sub>22</sub>, the same model - same space group pair (W : P4/nnc : q1̄q1 P : I4<sub>1</sub>/amd : 11̄ss), same atom positions and modulation waves - was used. The refinements converged rapidly, showing that the presented structure model is very general, and may well be applicable to any Nowotny chimney-ladder phase.</p>}},
  author       = {{Rohrer, F. E. and Lind, H. and Eriksson, L. and Larsson, A. K. and Lidin, S.}},
  issn         = {{0044-2968}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{11}},
  pages        = {{650--660}},
  publisher    = {{Oldenbourg Verlag}},
  series       = {{Zeitschrift fur Kristallographie}},
  title        = {{On the question of commensurability - The Nowotny chimney-ladder structures revisited}},
  url          = {{http://dx.doi.org/10.1524/zkri.2000.215.11.650}},
  doi          = {{10.1524/zkri.2000.215.11.650}},
  volume       = {{215}},
  year         = {{2000}},
}