Photon Factory Activity Report 2014 #32 (2015) B

AR-NE7A/2014G012

Trial Measurement of Liquid Density at NE7A
Kazuhiro Fuchizaki1,* Nozomu Hamaya2
Akio Suzuki3, Yoshihisa Mori4 and Takumi Kikegawa5
1
Department of Physics, Ehime University, Matsuyama 790-8577, Japan
2
Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan3
Department of Earth and Planetary Material Sciences, Tohoku University, Sendai 980-8578, Japan
4
Department of Applied Science, Okayama University of Science, Okayama 700-0005, Japan
5
Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
A suitable modification was made for MAX-III, a multianvil press installed at NE7A, KEK-AR, to measure density ofliquids utilizing x-ray absorption. Further improvement for quantitative measurements is now in progress.
1 Introduction
Measurement of density for non-crystalline substances,such as in a liquid or an amorphous state, is by far anontrivial problem. We have tried to detect a change indensity upon the phase transition in polyamorphs.
Our study revealed that tin tetraiodide exhibits thewater-type polyamorphism. [1,2] It should be emphasizedthat the liquid-liquid critical point (LLCP) is highly
expected to be located in the region centered at around
1.3 GPa and 1000 K. It is still necessary, however, forclaiming that SnI4’s LLCP is located above the melting
point of the crystalline phase, to detect an abrupt change
in density upon compression, although we have verified
the difference in density, which amounts to only about 0.4
g/cc, between the two liquid phases. [3]These findings were achieved by the x-ray absorption
measurements utilizing the facility installed in SPring-8.
Conducting a similar experiment also at the beamlines inKEK would bring considerable benefits to the highpressure community. This was our initial motivation forundertaking the present study.
2 Experiment
As a trial, we planned to modify the experimental setup
of NE7A station of KEK-AR, where a multianvil press,
MAX-III, is installed for high-pressure and temperatureexperiment. The first essential modification wasmounting two ion chambers (ICs) just in front of andbehind the press to measure the incident and thetransmitted x-ray intensities, I0 and I, respectively (Figs. 1and 2).
Switching the imaging plate (IP) already equipped withthe couple of ICs allows us to measure almost
simultaneously x-ray absorption as well as diffraction. It
then makes us possible to determine the absolute value
for density from a measurement in a solid state.
As depicted in Fig. 3, the sample assembly is a typical
one that is used in high-pressure experiments. It should be
noted that the sample is located exactly at the mid-pointin vertical direction. A gap between anvil blocks becomesnarrower with increasing load than the diameter of thesample container. In order for the sample to be scanned
across an x-ray beam, a ditch was made at the center on

the anvil surface. The sample has to be located at theheight of the ditch.

Fig. 1: The design allowing x-ray absorption anddiffraction by switching the ICs and the IP.

Fig. 2: A close view of the sample stage from theincident-beam side. The IC on this side is I0 in Fig. 1, andthe IC on the other side is I. Anvil blocks are seen
between the two ICs.
3 Results and Discussion
Figure 4 shows the absorption profiles obtained on afirst trial. The incident beam was monochromatized to0.2755 Å. The distortion of the profiles was found to be
more or less improved by resetting the sample. Using themethod described in [3], we could obtain at 2.2 GPa androom temperature (RT) the value, 3.94(17) g/cc, fordensity, which is appreciably smaller than 5.31 g/cc
obtained through diffraction. The large discrepancy isascribable to the ambiguity of the edge in the profile
originating from the beam divergence in transvers
direction. The latter effect is being tried to bedeconvoluted. We also expect that a method based on thePhoton Factory Activity Report 2014 #32 (2015) B

maximum entropy method [4] will be effective for theestimation of the location of the edge.

Fig. 3: Sample assembly used in the present experiment.

AR-NE7A/2014G012
beam time was provided in the latter
half period of thatyear. A follow-up experiment has just been carried out,
and much progress has been made. This was brought
about by the improvement in the system of running gears
to drive the press stage. Professor A. Suzuki took care ofthis improvement. Software with which to drive thesystem was prepared by Professor Y. Mori. The results
obtained from the last measurement will be reported inthe near future.
Acknowledgement
Preparations for the experiments were carried out using
the facility at the Geodynamics Research Center, Ehime
University. This work was supported by KAKENHI(Grant No. 26400398), and by a discretionary fund of theDean of the Faculty of Science, Ehime University.
References[1] K.Fuchizaki et al., J. Chem. Phys. 130, 121101 (2009).
[2] K.Fuchizaki et al., J. Chem. Phys. 135, 091101 (2011).
[3] K.Fuchizaki et al., J. Phys. Soc. Jpn. 82, 033003(2013).
[4] K.Fuchizaki et al., J. Chem. Phys. 127, 064504 (2007).
* fuchizak@phys.sci.ehime-u.ac.jp

Fig.4: The ratio, I/I0, is plotted as a function ofdisplacement, y, perpendicular to the beam axis.
Table 1: Density of liquid SnI4 obtained from theabsorption profiles shown in Fig. 1.
temperature (K)density (g/cc)
RT
3.94(17)600
4.32(19)800
4.47(8)The x-ray absorption profiles obtained at othertemperatures were similarly processed. The resultingdensity (including the one at RT) is listed in Table 1.
Unusual temperature dependence is readily noticeable;
the density increases with temperature. This unusual
behavior should be ascribed not to intrinsic nature ofliquid SnI4 but to the quality of the profile. Anotherimportant reason of the poor reproducibility of the density
at RT is the asymmetric feature. The profile should besymmetric in y-direction, and the analysis was madeassuming the symmetry. As clear from Fig. 1, the profile
recovered the expected symmetry with increasing
temperature. It is anticipated in this context that thedensity at 800 K is close to the actual density. At 1000 K,
however, the profile became irregular again. This
happened because the cover (made of PBN, see Fig. 3) ofthe sample container penetrated into the measuring point.
The present project started in November, 2013. The
measurement under the present proposal was done during
June 14 through 17, 2014. Unfortunately, however, no