Washington, DC, 13 February 2018—The diamond anvil cell (DAC) is a major tool that squeezes small samples between two opposing diamonds to generate high static pressures. It has been used for almost 60 years and holds the static pressure record generated in laboratories on the earth. After the milestone work pioneered by Peter M. Bell and Ho-kwang “Dave” Mao on the improvement of DAC designs and the DAC techniques at Geophysical Lab back in the 1970s, plenty of high profile research works have been done in the pressure region in excess of 1 million atmosphere pressures (100 GPa). Nowadays by using a beveled diamond anvil cell, researchers can generate as high as 400 GPa - the generally accepted limit pressure of a conventional DAC. However, although some studies have demonstrated techniques to generate 400 GPa, few have examined how the DAC behaves up to this pressure region.

Using submicron synchrotron x-ray beam, a group of scientists led by the Geophysical Laboratory's Ho-kwang “Dave” Mao, have studied the loading behavior of the DAC up to 400 GPa. In situ high-pressure synchrotron X-ray diffraction and absorption experiments have been done to investigate the behavior of the DAC. This study provides a detailed picture of pressure loading and distribution, gasket thickness variation, and diamond anvil deformation up to 400 GPa. The detailed results are reported in Proceeding of the National Academic of Sciences, USA.

Other team members including Bing Li, Cheng Ji, Wenge Yang, and Junyue Wang of the Geophysical Laboratory, Carnegie Institution of Washington; Ke Yang of Shanghai Synchrotron Radiation Facility; Ruqing Xu, Wenjun Liu and Zhonghou Cai of Advanced Photon Source; and Jiuhua Chen of the Center of High Pressure Science and Technology Advanced Research, China.

“Our work shows very details on the loading behavior of diamond anvils under enormous pressures, it would be very useful for high pressure scientists to obtain ultra-high pressure using DAC.” said Dr. Bing Li, the first author on the study.

“The s-shape loading curve and cupping in both beveled and flat anvils are universal and unavoidable consequences of conventional DAC experiments,” explained Dr. Mao, “our findings can be used to improve future DAC designs and benefit the high-pressure research in the region of 400 GPa”

Caption: X-ray imaging reveals diamond anvils cupping under extreme pressures. Image courtesy of Bing Li.

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