High-Pressure Third-Order Elastic Constants of MgO Single Crystal: First-Principles Investigation.

High-pressure third-order elastic constants of materials have rarely been investigated experimentally and theoretically to date, so the predictive ability of the method of the volume-conserving, homogeneous deformations based on the first-principles total-energy calculations is tested for the first time in this work. Using this approach, the high-pressure third-order elastic constants C 111 − 3 C 112 + 2 C 123 ${C_{111}}-3{C_{112}}+2{C_{123}}$ , C 111 / 2 + 3 C 112 + C 123 ${C_{111}}/2+3{C_{112}}+{C_{123}}$ , C 144 − C 155 ${C_{144}}-{C_{155}}$ , and C456 of the MgO single crystal are obtained successfully. Meanwhile, the reliability of this method is also verified by comparing the calculated structural properties and high-pressure second-order elastic constants of the MgO single crystal with the available experimental results and other theoretical predications. Results not only indicate the accuracy of our calculations but also reveal the feasibility of the present theoretical method. It is hoped that the present theoretical method and predictions on the high-pressure third-order elastic constants of the MgO single crystal would serve as a valuable guidance or reference for further related investigations. [ABSTRACT FROM AUTHOR]