Quartzlike carbon dioxide: An optically nonlinear extended solid at high pressures and temperatures

An extended-solid phase, carbon dioxide phase V (CO2-V), was synthesized in a diamond anvil cell by Laser heating the molecular orthorhombic phase, ca rbon dioxide phase III, above 40 gigapascals and 1800 kelvin. This new mate rial can be quenched to ambient temperature above 1 gigapascal. The vibrati on spectrum of CO2-V is similar to that of the quartz polymorph of silicon dioxide, indicating that it is an extended covalent solid with carbon-oxyge n single bonds. This material is also optically nonlinear, generating the s econd harmonic of a neodymium-yttrium-lithium-fluoride Laser at a wavelengt h of 527 nanometers with a conversion efficiency that is near 0.1 percent.