Photon Factory Activity Report 2005 #23 Part B (2006)
High Pressure Science

NE5C/2005G138

Structure of liquid IV-VI compounds under pressure
Kazuhiko TSUJI*, Masatoshi TOMOMASA, Takuya HIGAKI, Takazumi HAYAKAWA,Andreas HINZMANN, Akiko YAMORI, Yoshiharu TAGAWA and Ayano CHIBA
Department of Physics, Keio Univ., 3-14-1, Hiyoshi, Kohoku, Yokohama 223-8522, Japan

Experimental
X-ray diffraction patterns were taken by an energydispersive method using the synchrotron radiation.
Pressure was generated by using the multi-anvil highpressure apparatus, MAX80, installed at AR-NE5C.
Results and Discussion
Example of the diffraction intensity of liquid GeTe atseveral pressures is shown in Fig. 1. Broad curve is thediffraction from the liquid and sharp peaks is thefluorescence x-rays and the diffraction peaks from thesample container.
With increasing pressure, the height of the subpeak at-1
about 4.6 A decreases while the change in the height and-1
the position of the first peak at about 3.5 A is small.
Drastic change was observed between 5.4 GPa and 6.6-1
GPa: A peak at about 2.5 A appears above 6.6 GPa. It
may suggest the drastic pressure-induced structuralchange in the low-dimensional network liquids. Detailed
analysis is in progress.

8.6GPa7.6GPa6.6GPacountsIntroduction
In order to elucidate the effects of the dimensionality of
the covalent bond network on the pressure dependence ofthe structure of liquids, we have investigated the structureof liquid IV-VI compounds under pressure. Recently wehave reported the pressure dependence of the localstructure of liquid III-V compounds [1-3] and liquid II-VI
compounds [4-6]. In liquid group 14 elements and liquid
III-V compounds with three-dimensional network ofcovalent bonds, a continuous structural change has beenobserved in a wide pressure region. On the other hand, inliquid CdTe, which has also three dimensional network
structure, with high ionicity in chemical bonding a sharp
structural change has been observed.
In the crystalline phase, GeTe crystallizes in therhombohedral structure at normal pressure and at room
temperature. It is reported that with increasing
temperature at normal pressure and with increasingpressure at room temperature, phase transitions occur tothe rocksalt structure. At high temperature, however,phase diagram has not been investigated.
Liquid group 15 elements and liquid IV-VI compounds
are known to have a structure with two-dimensional
network of bonding. They consist of two kinds ofbonding; strong and relatively weak bonding. With
increasing pressure, it is expected that the difference
between these bonding decreases. It is interesting toinvestigate the pressure dependence of the local structureof liquid IV-VI compounds and compare the results withthose of other liquids.

5.4GPa

5.0GPa4.2GPa3.5GPa2.2GPa0246810-1

Q /AFig. 1. Example of the diffraction intensity of liquid
GeTe at several pressures.
References[1] T. Hattori et al., Phys. Rev. B 68, 224106 (2003).
[2] T. Hattori et al., J. Phys.: Condens. Matter 16, S997
(2004).
[3] T. Hattori et al., Phys. Rev. B72, 064205 (2005).
[4] T. Kinoshita et al., Phys. Rev. B 72, (2005) 060102R1-4.
[5] T. Hattori et al., Phys. Rev. B 73 (2006) 054203-1-9.
[6] T. Narushima et al., Proc. 20th AIRAPT Conference,Karlsruhe, 2005, T2-O80.
* tsuji@phys.keio.ac.jp

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