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

NE5C/2004G046

Structure of liquid II-VI compounds under pressure
Kazuhiko TSUJI*, Masatoshi TOMOMASA, Takuya HIGAKI, Ayano CHIBA,Takashi NARUSHIMA, and Takanori HATTORI
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 DiscussionThe static structure factors, S(Q) of liquid II-VI
compounds at several high pressures are shown in Fig. 1.
We can see the similarity in the shape of S(Q) amongliquid ZnSe, liquid CdTe and liquid HgTe [4-6].
The pair distribution functions, g(r) was obtained by theFourier transformation of S(Q). The value of r1, the firstpeak of g(r) of liquid ZnSe at 1.7 GPa and 4.3 GPa isalmost the same as the value of crystalline ZnSe withzincblende structure. For liquid CdTe below 2 GPa, it isalmost the same as its crystalline value with thezincblende structure and above 2GPa it is almost the sameas its crystalline value with the rocksalt structure. Forliquid HgTe, at low pressure it is almost the same as its
crystalline value with the rocksalt structure and increases
with increasing pressure.
From the comparison of the pressure dependence ofS(Q) and g(r) it is concluded that the pressure dependenceof the local structure is alike among liquid HgTe, CdTeand ZnSe, although the pressure width where structuralchanges occur is different. The local structure changes
from the zincblende-like structure to the rocksalt-likestructure and then to another high-pressure form. The
pressure dependence of the local structure of liquidcompounds with high ionicity in the bonds is similar to
those of crystals. This is in contrast with the quite
different pressure dependence of the local structure ofliquids from that in the crystals with less ionicity in thebonds.
For liquid HgTe, the structural change occurs
continuously in contrast with the sharp change in liquid
CdTe. This may be related to the presence of the182

Users' Reportintermediate structures between the zincblende structure
and the rocksalt structure and above the rocksalt structure.

HGF

E
S(Q)

Introduction
In order to elucidate the effects of the ionicity inchemical bonding on the structure of covalent liquids, wehave investigated the structure of liquid II-VI compounds;
liquid CdTe, liquid HgTe and liquid ZnSe under pressure.
Recently we reported the structure of liquid III-Vcompounds; liquid GaSb [1], liquid InAs [2] and liquidInSb [3] under pressure. The ionicity of the chemicalbonding of II-VI compounds is higher than that of these
III-V compounds.

DCB
1A

100246810Q / A -1Fig. 1. S(Q) of liquid II-VI compounds. A: liquid ZnSeat 1.7 GPa, B: liquid ZnSe at 4.3 GPa, C: liquid ZnSe at
5.5 GPa, D: liquid ZnSe at 7.3 GPa, E: liquid CdTe at 0.5GPa, F: liquid CdTe at 3.0 GPa, G: liquid HgTe at 0.3GPa and H: liquid HgTe at 8 GPa.
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