Abstract
The behaviour of the lattice parameters of HTCuCN (high-temperature form), AgCN and AuCN have been investigated as a function of temperature over the temperature range 90-490 K. All materials show one-dimensional negative thermal expansion (NTE) along the -(M-CΞN)- chain direction c (α c(HT-CuCN)= -32.1 × 10-6 K1, αc(AgCN)= -23.9 × 10-6 K1 and αc(AuCN) = -9.3 × 10-6 K-1 over the temperature range 90-490 K). The origin of this behaviour has been studied using RMC modelling of Bragg and total neutron diffraction data from AgCN and AuCN at 10 and 300 K. These analyses yield details of the local motions within the chains responsible for NTE. The low-temperature form of CuCN, LT-CuCN, has been studied using single-crystal X-ray diffraction. In this form of CuCN, wavelike distortions of the -(Cu-CΞN)- chains occur in the static structure, which are reminiscent of the motions seen in the RMC modelling of AgCN and AuCN, which are responsible for the NTE behaviour.
Original language | English |
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Pages (from-to) | 457-462 |
Number of pages | 6 |
Journal | Zeitschrift fur Kristallographie |
Volume | 225 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2010 |
Externally published | Yes |
Funding
Acknowledgments. The authors thank the EPSRC for Research Studentships for GBW, AHP and EJB and for a single-crystal X-ray diffractometer in Reading (Grant No. EP/533526/1). The University of Reading is acknowledged for provision of the Chemical Analysis Facility.
Keywords
- Negative thermal expansion
- One dimensional structure
- Pair distribution function (PDF)
- Reverse Monte Carlo (RMC)
- Transition-metal cyanide