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Isotropic Negative Thermal Expansion in β-Si(NCN)2and Its Origin

Kroll, Peter and Andrade, Miria and Yan, Xuehua and Ionescu, Emanuel and Miehe, Gerhard and Riedel, Ralf (2012):
Isotropic Negative Thermal Expansion in β-Si(NCN)2and Its Origin.
In: The Journal of Physical Chemistry C, 116 (1), ACS, pp. 526-531, ISSN 1932-7447,
[Online-Edition: http://dx.doi.org/10.1021/jp2106583],
[Article]

Abstract

Ab initio molecular dynamic simulations and high-temperature synchrotron crystallography show that β-Si(NCN)2 exhibits isotropic negative thermal expansion from 500 to 1123 K over its entire temperature stability range. The experimental value of the linear expansion coefficient changes from α = −1.24 × 10–6 K–1 at 500 K to α = −1.93 × 10–6 K–1 at 1123 K. Examination of vibrational motions locate the effect to transverse vibrations of carbodiimide fragments bridging between Si atoms (Si–N═C═N–Si). A detailed atomistic analysis reveals that the roto-vibrational movements of the bridging NCN units resemble that of a centrifugal governor pulling together the crystal framework upon temperature increase.

Item Type: Article
Erschienen: 2012
Creators: Kroll, Peter and Andrade, Miria and Yan, Xuehua and Ionescu, Emanuel and Miehe, Gerhard and Riedel, Ralf
Title: Isotropic Negative Thermal Expansion in β-Si(NCN)2and Its Origin
Language: English
Abstract:

Ab initio molecular dynamic simulations and high-temperature synchrotron crystallography show that β-Si(NCN)2 exhibits isotropic negative thermal expansion from 500 to 1123 K over its entire temperature stability range. The experimental value of the linear expansion coefficient changes from α = −1.24 × 10–6 K–1 at 500 K to α = −1.93 × 10–6 K–1 at 1123 K. Examination of vibrational motions locate the effect to transverse vibrations of carbodiimide fragments bridging between Si atoms (Si–N═C═N–Si). A detailed atomistic analysis reveals that the roto-vibrational movements of the bridging NCN units resemble that of a centrifugal governor pulling together the crystal framework upon temperature increase.

Journal or Publication Title: The Journal of Physical Chemistry C
Volume: 116
Number: 1
Publisher: ACS
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 04 Apr 2012 07:37
Official URL: http://dx.doi.org/10.1021/jp2106583
Identification Number: doi:10.1021/jp2106583
Funders: German Science Foundation under the Priority Program SPP 1236 “Strukturen und Eigenschaften von Kristallen bei extrem hohen Drücken und Temperaturen”, Fonds der Chemischen Industrie, P.K. is supported by the NSF (DMR-0907117) and by the U.S. AFOSR and NASA under the National Hypersonics Science Center for Materials and Structures (AFOSR Contract No. FA9550-09-1-0477), The computational work was made possible through generous grants by the Texas Advanced Computing Center in Austin, TACC, Texas, and by the High Performance Computing Center at UTA
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