CAREER: Chemical Trends of Elements Under Pressure and their Effects to Forms and Properties of Materials

The University Corporation, Northridge, Northridge CA

Investigators

Abstract

NONTECHNICAL SUMMARY This CAREER award supports research and education in designing novel materials by understanding the basic chemical characteristics of elements under high pressure. All matter is composed of elements, and all elements show peculiar chemical properties depending on their positions in the periodic table. A general rule of chemistry is that the characteristics and behaviors of elements are determined by electrons of an atom's outermost orbital. Our current knowledge and practice of chemistry has been limited by the number of elements in the periodic table and the chemical states in which these elements could exist. This project aims to reveal how physical forces can be used to break the above boundary of chemistry. When this happens, the existing elements can drastically change their chemical characteristics and identities and behave like entirely new elements. Using advanced computational techniques, this project will systematically explore the new materials that can be formed by utilizing the physical pressures that alter the chemical properties of elements. Combining with a new quantum mechanics model of atoms in confined space, this project will apprehend how the pressure will transform the periodic table of elements. The work may largely extend the scope of materials by revealing the transformation of elements under pressure. It may also give rise to knowledge of how the new chemistry can be utilized in designing and obtaining new materials with unusual properties as well as in understanding the behavior and distribution of elements in the interior of Earth and extraterrestrial planets. The computer simulations of atomic and electronic structures will be incorporated into the early curriculum of undergraduate and graduate students in California State University Northridge, a minority serving institution with a large Hispanic enrollment. It will also be introduced to local community college and high school students, providing them with a deeper understanding of materials and chemistry and new skills and tools for their future careers. TECHNICAL SUMMARY This CAREER award supports computational and theoretical research aimed to advance the design and discovery of materials by understanding how the basic chemical character of elements, such as reactivity or oxidation state, can change under pressure and how to utilize this knowledge to make materials with unusual and desired properties. This plan is inspired by a series of striking phenomena uncovered by recent high-pressure research, such as core electrons that become reactive and form chemical bonds, electrons that play the role of anions at the interstitial sites, and noble gases that react with ionic compounds without forming any chemical bond. These phenomena are exciting because they not only alter the chemistry at the very fundamental level, but also can greatly broaden the form and the properties of materials. An in-depth and systematized understanding of how elements behave under different levels of pressure is essential but not yet in place. This emerging area of materials under extreme conditions is difficult to directly study using current high-pressure experiments, and these methods are also time consuming and costly. Rapid and low-cost computer simulation can explore high pressure and have potential to provide guidance to experiment. The PI will employ computer simulations based on quantum mechanics and automatic crystal structure search methods to address these issues by studying the stability and bonding features of a series of compounds containing focused elements. Specifically, the PI will undertake the following research objectives, exploring: 1) the reactivity of inner core p and d core electrons and its relation to external pressures, and the corresponding bonding feature and the properties; 2) a reverse chemistry phenomena of binary 3d metal compounds; 3) the use of the novel chemistry under pressure in designing and producing new materials with superlative properties; 4) the possibility of representing the chemical behavior of elements under different levels of pressure by a small set of parameters, especially whether and how the periodic table changes under high pressure. The project integrates research and education through a set of activities including establishing a new computational materials course and lab; training and involving students in cutting edge materials research; and organizing lunch forums and seminars. Furthermore, selected students in other CSUN research groups will be invited to work as guest researchers and integrate computational methods into their own research topics. The educational plan will help increase the involvement of students who are underrepresented in STEM areas. It includes outreach activities to provide students from underrepresented groups with multiple opportunities to explore materials science research, STEM education, and associated educational and professional pathways. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.