College of Engineering News • Iowa State University

Levitas and Feng suggest new approach for high pressure research

Valery Levitas, Schafer Professor and faculty member of aerospace engineering and mechanical engineering as well as faculty scientist at Ames Laboratory, and his postdoctoral researcher Biao Feng (currently, at Los Alamos National Laboratory) suggest a new approach for increasing the highest achievable pressure for scientific research.

Currently, the highest possible static pressure is produced by compressing a thin sample/gasket by two diamond anvils in a diamond anvil cell. In high pressure

Valery Levitas and Biao Feng

research, one of the goals is to reach the highest possible pressure in order to explore material behaviors and find new phases. Another objective is to achieve medium-high pressure without breaking diamonds, so they can be reused multiple times during physical experiments.

The two theoretically suggested a new approach of how to increase the maximum achievable pressure without breaking anvils. They found conditions at which very high pressure gradient and, consequently, high pressure can be achieved in a region near the center of a sample. The revealed phenomenon of generating extremely high pressure gradient is called the pressure self-focusing effect. They also found that the superposition of torsion in a rotational diamond anvil cell offers drastic enhancement of the pressure self-focusing effect and allows one to reach much higher pressure under the same force and deformation of anvils.

(a) Rotational diamond anvil cell scheme, (b) a quarter of the sample and anvil in the initial undeformed state and the geometry of anvil, and (c) the geometry of sample in the undeformed state.

Levitas and Feng expect that experimentalists will be motivated to test their proposal for an increasing pressure gradient and maximum pressure.

The research was published in the Scientific Reports of Nature Publishing Group.

Feng B. and Levitas V.I. Pressure self-focusing effect and novel methods for increasing the maximum pressure in traditional and rotational diamond anvil cells.

Scientific Reports, 2017, Vol. 7, 45461.

Detailed theory and finite element simulations of the plastic flow under extremely high pressure in rotational diamond anvil cells was published in International Journal of Plasticity, the highest rank mechanics journal:

Feng B. and Levitas V.I. Large elastoplastic deformation of a sample under compression and torsion in a rotational diamond anvil cell under megabar pressures. Int. J. Plasticity, 2017, DOI 10.1016/j.ijplas.2017.03.002, 17 pages.