Regular Article

Investigation of melting point, Debye frequency and temperature of iron at high pressure

¹ Tan Trao University, Km 6, Yen Son, Tuyen Quang 301910, Vietnam
² Institute of Research and Development, Duy Tan University, 03 Quang Trung, Hai Chau, Da Nang 550000, Vietnam
³ Faculty of Natural Sciences, Duy Tan University, 03 Quang Trung, Hai Chau, Da Nang 550000, Vietnam
⁴ Hanoi Pedagogical University No2, Nguyen Van Linh, Vinh Phuc 15900, Vietnam
⁵ Hong Duc University, 565 Quang Trung, Dong Ve, Thanh Hoa 441430, Vietnam
⁶ VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi 120000, Vietnam
⁷ Laboratory of Advanced Materials Chemistry, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
⁸ Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam

^a e-mail: tranthiha@tdtu.edu.vn

Received: 14 February 2020
Received in final form: 17 April 2020
Published online: 22 June 2020

Abstract

The Debye model has been developed to investigate the pressure effects on melting point, Debye frequency and Debye temperature of iron metal. The analytical expressions of these thermodynamic quantities have been derived as functions of crystal volume compressibility. The pressure dependence of them is studied based on the well-established equation-of-state which includes the contributions of the anharmonic and electronic thermal pressures. We performed numerical calculations for iron up to pressure 350 GPa and compared with experimental data when possible. Our results show that the Debye frequency and Debye temperature increase rapidly with compression, and beyond 150 GPa they behave like linear functions of pressure. From the pressure-dependent melting point of iron, we deduce the temperatures of the Earth’s inner-outer core boundary (ICB) and core-mantle boundary (CMB). The temperatures of the Earth’s ICB and CMB are predicted lower than 5540(±170) K and about 4060 K, respectively.