Pressure Dependence on Ruby Bond Length Based on First-Principles Band-Structure Calculations
Mega Novita (a*), Nur Cholifah (b), Kazuyoshi Ogasawara (c)
a) Faculty of Engineering and Informatics, Universitas PGRI Semarang, Jl. Sidodadi-Timur No.24 Semarang, Central Java 50232, Indonesia
*novita[at]upgris.ac.id
b) Lembaga Penelitian dan Pengabdian Kepada Masyarakat, Universitas PGRI Semarang, Jl. Lontar No.1 Semarang, Central Java 50232, Indonesia
c) School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen Sanda, Hyogo 669-1337 Japan
Abstract
Ruby, or the trivalent chromium ion activated in alumina crystal ((alpha)-Al(_{2})O(_{3}): Cr(^{3+})), needless to say, is a beautiful gemstone and known as the first solid-state laser in history. The so-called "ruby pressure scale" using its fluorescence lines is particularly popular in high-pressure science because of the simplicity and the accuracy of optical measurements in the diamond-anvil cell (DAC) experiments. Therefore, here performed first-principles band-structure calculations on the effect of external pressure on ruby bond length without referring to any experimental parameter. Cambridge Serial Total Energy Package (CASTEP) code was utilized to estimate the lattice relaxation effect as the external pressure applied which results in the ruby bond length. Firstly, we carried out the structural optimization of the pure (alpha)-Al(_{2})O(_{3}) crystal and then followed by the geometry optimization of (alpha)-Al(_{2})O(_{3}): Cr(^{3+}). The results show that Al-O bond lengths of the pure (alpha)-Al(_{2})O(_{3}) crystal and Cr-O bond lengths of (alpha)-Al(_{2})O(_{3}): Cr(^{3+}) decreased as the applied pressure increased.
Keywords: pressure, first-principles, CASTEP, a-Al2O3
Topic: Material Science