Quasi–Ab InitioMolecular Dynamic Study of Fe Melting

Abstract

We have investigated the melting of hcp Fe at high pressure by employing molecular dynamics simulations in conjunction with the full potential linear muffin tin orbital method. Apart from being of fundamental value, the melting of iron at high pressure is also important for our understanding of the Earth. The subject of iron melting at high pressures is controversial. The experimental data for the iron melting temperature can be separated into two regions, "low" and "high." Here we present an ab initio simulated iron melting curve which is in agreement with the low temperatures at lower pressures, but is in excellent agreement with the high-mostly shockwave-temperatures at high pressures. A comparison with available data lends support to the presented iron melting curve.

Quenching of bcc-Fe from high to room temperature at high-pressure conditions: a molecular dynamics simulation

“…The EAM melting temperature is in agreement with the shock-wave data [3] at a pressure of 243 GPa ( figure 1). The most recent melting data by Ma et al [19] was predicted almost exactly back in 2000 [6]. Therefore, we are confident in this method.…”

“…That discovery [3] was not confirmed by later shock-wave experiments [4]; however, the difference in compositions of iron samples could be the reason for that (see [5] for discussion). It was suggested, on the basis of non-empirical [6] molecular dynamics (MD) simulations, that under high pressure iron transforms on heating to the body-centered cubic (bcc) phase [7]. A number of IC properties can be explained within the paradigm of the bcc iron phase stability under the IC PT conditions, such as the low shear modulus [8,9] and elastic anisotropy [10].…”

“…Fe atoms interacted via the embedded-atom model (EAM) potential [6] parameterized solely on the basis of first principles calculations, without any experimental data. This EAM has been proved to perform very well.…”

“…The 3D periodic boundary conditions were applied. The details of simulations are the same as reported earlier [6]. The timestep in our simulations was 1 fs.…”

Ab initiobased empirical potential used to study the mechanical properties of molybdenum

“…We follow the approach of Belonoshko et al, 68 in which constant-NPT MD simulations determine the melting temperature. Simulations with about 16,500 atoms run for 500,000 steps with a 1 fs time step.…”