Ab initio calculations of structural and magnetic phases of iron
Martin Friák and Mojmír Šob
Iron is located between antiferromagnetic and ferromagnetic regions in the periodic table. This location allows for a variety of magnetic structures and magnetic effects and plays a crucial role for the phase stability of iron and iron-based systems. Ferromagnetic body-center cubic (bcc) iron undergoes a phase transition to non-spin-polarized hexagonal closed-packed (hcp) phase at a pressure of about 13 GPa [1]. From geological point of view, high-pressure phases of iron are very exciting as iron is the dominant component of the Earth's core and a proper understanding of the physics of planetary deep interior requires information on its properties. Yet, the ground state of iron is not identified even in the region of relatively low pressures, from 15 to 50 GPa. Scientific importance of elevated-pressure iron studies has grown recently after a superconducting phase in hcp Fe under pressure was found experimentally by Shimizu [2]. Physical origin of the superconductivity occurring between 15 GPa and 30 GPa is still not fully understood. Recent studies of a role of the electron-phonon coupling [3] and both the ferromagnetic and antiferromagnetic fluctuations [4] raised the question of a magnetic ordering in hcp iron.
- Schematic drawing of the transofrmation path [5,6] connecting the bcc and hcp structures using four-atomic unit cell (atoms are numbered 1-4).
The purpose of the project is to examine, from first principles, the structural and magnetic behavior of different iron states along the bcc-hcp transformation path [5,6] at various volumes. The calculated total energies are used to predict the structural phase and magnetic ordering minimizing the total energy for a given volume and proceeding along the transformation path. The stable and metastable states may hence be identified and the phase boundaries between various iron modifications may be determined similarly as in case of the bcc-fcc transformation path [7].
<a href="http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRBMDO000077000017174117000001&idtype=cvips&gifs=yes">The results may be found published in Phys. Rev. B 77, 174117 (2008). </a>
References
<typolist type="1">
F. Wang and R. Ingalls, Phys. Rev. B 57, 5647 (1998).
K. Shimizu, T. Kimura, S. Furomoto, K. Takeda, K. Kontani, Y. Onuki, and K. Amaya, Nature 412, 3169 (2001).
S. K. Bose, O. V. Dolgov, J. Kortus, O. Jepsen, and O. K. Andersen, Phys. Rev. B 67, 214518 (2003).
I. I. Mazin, D. A. Papaconstantopoulos, and M. J. Mehl, Phys. Rev. B 65, 100511 (2002).
M. Šob, M. Friák, L. Wang, and V. Vitek, in Multiscale Modelling of Materials, edited by V. Bulatov, T. D. de Rubia, R. Phillips, E. Kaxiras, and N. Ghoniem (MRS Symposium Proc., 1999), vol. 538, pp. 523-527.
M. Šob, M. Friák, L. Wang, and V. Vitek, in Proc. Int. Conf. on Solid-Solid Phase Transformations '99 (JIMIC-3), edited by M. Koiwa, T. Otsuka, and T. Miyazaki (The Japan Institute of Metals, Sendai, 1999), pp. 855-858.
M. Friák, M. Šob, V. Vitek, Phys. Rev. B 63, 052405 (2001).
</typolist>
Phase stability and mechanical properties of biocompatible Ti-alloys
First-Principles Study of the Carbon-Carbon Interaction in Iron
