Инд. авторы:	Sagatov N.E., Sagatova D.N, Gavryushkin P.N., Litasov K.D.
Заглавие:	Fe-N System at High Pressures and Its Relevance to the Earth's Core Composition
Библ. ссылка:	Sagatov N.E., Sagatova D.N, Gavryushkin P.N., Litasov K.D. Fe-N System at High Pressures and Its Relevance to the Earth's Core Composition // Crystal Growth & Design. - 2021. - Vol.21. - Iss. 11. - P.6101-6109. - ISSN 1528-7483. - EISSN 1528-7505.
Внешние системы:	DOI: 10.1021/acs.cgd.1c00432; WoS: 000715841000011;
Реферат:	eng: Based on ab initio calculations within the density functional theory and crystal structure prediction algorithms, the structure and stability of iron-nitrogen compounds in the pressure range of 100-400 GPa and temperatures up to 4000 K were determined. Three new iron nitrides Fe4N3-Imm2, Fe2N-Pnma, and Fe3N-C2/m were predicted. Fe4N3 was shown to be stable at pressures up to 266 GPa and then decompose into Fe2N + 2FeN. Predicted Fe2N-Pnma becomes stable with respect to the decomposition reaction 9Fe(2)N = Fe4N3 + 2Fe(7)N(3) at pressures above 221 GPa. Fe3N-C2/m stabilizes with respect to decomposition into 2Fe + Fe7N3 at pressures above 265 GPa. Also, it was shown that beta-Fe7N3 synthesized in diamond anvil cell experiments has an orthorhombic Pbca structure, and at pressures above similar to 320 GPa decomposes into 2Fe(2)N + Fe3N. All predicted Fe-rich iron nitrides, except Fe4N3-Imm2, have structural analogs among iron carbides. Considering the temperature effect, we observed that FeN-P2(1)3, Fe2N-Pnma, and Fe3N-C2/m can be stable at the Earth's inner core pressures and temperatures up to 4000 K, whereas Fe4N3-Imm2 and beta-Fe7N3 are thermodynamically unstable in the entire studied temperature range. Although Fe7N3-Pbca is thermodynamically unstable at inner core pressures, it shows the closest coincidence of the S- and P-wave velocities with seismic observations among the studied Fe-nitrides. Overall, Fe-nitrides cannot be the major compounds in the inner core of the Earth and can only substitute other elements such as carbon in Fe-carbides in minor amounts.
Ключевые слова:	MANTLE; CRYSTAL; HARDNESS; PREDICTION; FE7C3; CARBIDES; NITROGEN; PHASE-RELATIONS; IRON NITRIDES; GPA;
Издано:	2021
Физ. характеристика:	с.6101-6109