Building zero isotherm of hydrogen isotopes taking into account experimental results of isentropic compression up to pressures of several megabar

An isentropic compression of substances using ultra-high magnetic field makes it possible to effectively reach 'cold' pressures of several megabar in a studied substance. The process is realized in a device based on magneto-cumulative generator MC-1. Arrangement of the experiments, where the isotherm of 'cold' compression of hydrogen isotopes is studied, is described in the paper. Results of preliminary data analysis obtained at solid protium and deuterium compression are also presented. Achieved densities correspond to the pressures higher than 5 Mbar. A method of zero isotherm building, taking into account gradient and thermal corrections, is described. Errors, with which positions of experimental points in P-ρ plane are determined, are associated mostly with a precision of sizes calculation of a reference and studied samples using x-ray image, obtained in the experiment. Deviations of the built points from the curve, extrapolating the experimental data on the diamond anvils to the multi-megabar range, lie within experimental errors. The zero isotherm, approximating the obtained nowadays-experimental data, is compared with several first-principles calculation results.