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Cell doubling in copper formate tetrahydrate at the antiferroelectric phase transition
Solid State Communications, Vol. 5, pp.887-888, 1967. Pergamon Press Ltd. Printed in Great Britain
CELL DOUBLING IN COPPER FORMATE TE ~RAHYDRATE AT THE ANTIFERROELECTRIC PHASE TRANSITION K. C. Turberfield Solid State Physics Division, A. E.R. E., Harwell, England (Received 29 September 1967 by C.W. McCombie)
Neutron diffraction data of the type (hO 1) has been taken using a single crystal of Cu (HCOO)24D20 at temperatures ranging from 4. 2°Kto -20°C. rhese show that the antiferroelectric phase transition involves a doubling of the unit cell along the c axis and also a modification of the space group.
COPPER formate tetrahydrate has been studied extensively over the last few years as it displays interesting antiferromagnetic and antiferroelectric order at 17°K and -38°C respectively. ~ X-ray and neutron diffraction studies 4of the show 4H20thecompound that crystal isat monoclinic room temperature with a space group P2~/a (in which reflections of the type (hOl) occur with h even and 1 even or odd). In the
were found to persist with no appreciable change in intensity. The strongest of these reflections (the ~04+) was then observed continuously while the temperature was allowed to rise. The peak decreases intensity remained abruptly constant by 5%. At until -28°C 38°C it again when it fell sharply, this-time to zero. These temperatures are those associated with the antiferroelectric phase transitions of Cu(HCOO) 24H20 and Cu(HCOO)24D20 respectively as shown by dielectric measurements. The 5% loss in intensity therefore indicates that deuteration of the water of crysallization was incomplete. The sharpness of the intensity drop is as expected for a first order phase transition. -
present work neutron diffraction data of the type (hOl) has been taken on a single crystal of Cu(HCOO)24D2 0 at temperatures ranging from -20°Cto 4. 2°K. At 4. 2°K strong reflections were observed in accordance with the room temperature diffraction data but in addition extra reflections occurred with h odd whose intensities were one to two orders of magnitude weaker. Also reflections with ha]! integral 1 indices were found in conjunction with both even and odd 1 indices having comparable weak intensities. On warming the crystal to ?7°Kall the extra reflections
These observations show that the orderIng process at the antiferroelectrl~ phase transition involves a cell doubling along the c axis and also a modification of the space group. Acknowledgement The experimental assistance of A. Rickman is gratefully acknowledged. -
References 1.
KOBAYASHI H. and HASEDA T.,
2.
KIRWAMA H.,
3.
OKADA K.,
J. Phys. Soc. Japan
18, 541 (1963).
Bull. Chem. Soc. Japan 35, 1199 (1962).
Phys. Rev. Letters 15, 252 (1965). 887
888
CELL DOUBLING IN COPPER FORMATE TETRAHYDRATE
4.
KIRIYAMA R.,
5.
OKADA K., KAY M.I., CROMER D.T. and ALMODOVAR I.,
IBAMOTO H. and MATSUO K.,
Acta. Cryst.
Vol. 5, No. 11
7, 482 (1954). J. Chem. Phys. 44, 1648 (1966).
Für einen Einkristall aus Cu(HCOO)2. 4D2 0 bei Temperaturen von 4, 2°K bis -20°C wurden Neutronenbeugungsmessungen des (hOl)-Typs durchgeftlhrt. Es ergibt sich, dass beim Ubergang in die antiferroelektrische Phase die Einheitszelle in Richtung der c-Achse verdoppelt wird und die Raumgruppe verändert wird.
CELL DOUBLING IN COPPER FORMATE TE ~RAHYDRATE AT THE ANTIFERROELECTRIC PHASE TRANSITION K. C. Turberfield Solid State Physics Division, A. E.R. E., Harwell, England (Received 29 September 1967 by C.W. McCombie)
Neutron diffraction data of the type (hO 1) has been taken using a single crystal of Cu (HCOO)24D20 at temperatures ranging from 4. 2°Kto -20°C. rhese show that the antiferroelectric phase transition involves a doubling of the unit cell along the c axis and also a modification of the space group.
COPPER formate tetrahydrate has been studied extensively over the last few years as it displays interesting antiferromagnetic and antiferroelectric order at 17°K and -38°C respectively. ~ X-ray and neutron diffraction studies 4of the show 4H20thecompound that crystal isat monoclinic room temperature with a space group P2~/a (in which reflections of the type (hOl) occur with h even and 1 even or odd). In the
were found to persist with no appreciable change in intensity. The strongest of these reflections (the ~04+) was then observed continuously while the temperature was allowed to rise. The peak decreases intensity remained abruptly constant by 5%. At until -28°C 38°C it again when it fell sharply, this-time to zero. These temperatures are those associated with the antiferroelectric phase transitions of Cu(HCOO) 24H20 and Cu(HCOO)24D20 respectively as shown by dielectric measurements. The 5% loss in intensity therefore indicates that deuteration of the water of crysallization was incomplete. The sharpness of the intensity drop is as expected for a first order phase transition. -
present work neutron diffraction data of the type (hOl) has been taken on a single crystal of Cu(HCOO)24D2 0 at temperatures ranging from -20°Cto 4. 2°K. At 4. 2°K strong reflections were observed in accordance with the room temperature diffraction data but in addition extra reflections occurred with h odd whose intensities were one to two orders of magnitude weaker. Also reflections with ha]! integral 1 indices were found in conjunction with both even and odd 1 indices having comparable weak intensities. On warming the crystal to ?7°Kall the extra reflections
These observations show that the orderIng process at the antiferroelectrl~ phase transition involves a cell doubling along the c axis and also a modification of the space group. Acknowledgement The experimental assistance of A. Rickman is gratefully acknowledged. -
References 1.
KOBAYASHI H. and HASEDA T.,
2.
KIRWAMA H.,
3.
OKADA K.,
J. Phys. Soc. Japan
18, 541 (1963).
Bull. Chem. Soc. Japan 35, 1199 (1962).
Phys. Rev. Letters 15, 252 (1965). 887
888
CELL DOUBLING IN COPPER FORMATE TETRAHYDRATE
4.
KIRIYAMA R.,
5.
OKADA K., KAY M.I., CROMER D.T. and ALMODOVAR I.,
IBAMOTO H. and MATSUO K.,
Acta. Cryst.
Vol. 5, No. 11
7, 482 (1954). J. Chem. Phys. 44, 1648 (1966).
Für einen Einkristall aus Cu(HCOO)2. 4D2 0 bei Temperaturen von 4, 2°K bis -20°C wurden Neutronenbeugungsmessungen des (hOl)-Typs durchgeftlhrt. Es ergibt sich, dass beim Ubergang in die antiferroelektrische Phase die Einheitszelle in Richtung der c-Achse verdoppelt wird und die Raumgruppe verändert wird.