Structural, elastic, and electronic properties of Fe3C from first principles

Abstract

Using first-principles calculations within the generalized gradient approximation, we predicted the lattice parameters, elastic constants, vibrational properties, and electronic structure of cementite (Fe 3 C). Its nine single-crystal elastic constants were obtained by computing total energies or stresses as a function of applied strain. Furthermore, six of them were determined from the initial slopes of the calculated longitudinal and transverse acoustic phonon branches along the [100], [010] and [001] directions. The three methods agree well with each other, the calculated polycrystalline elastic moduli are also in good overall agreement with experiments. Our calculations indicate that Fe 3 C is mechanically stable. The experimentally observed high elastic anisotropy of Fe 3 C is also confirmed by our study. Based on electronic density of states and charge density distribution, the chemical bonding in Fe 3 C was analyzed and was found to exhibit a complex mixture of metallic, covalent, and ionic characters. *Corresponding author: chao@lanl.gov

A first-principles study of cementite (Fe3C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

“…Our calculated values are in good agreement with previously calculated C ij s of Fe 3 C. 37,38 However, Lv et al 39 reported that C 44 is negative. Barring any typographical error, their C ij values of predict that Fe 3 C is elastically unstable, which is inconsistent with both present and previous calculations.…”

“…Barring any typographical error, their C ij values of predict that Fe 3 C is elastically unstable, which is inconsistent with both present and previous calculations. 37,38 Recently, Grimvall et al 68 have discussed the issue of elastic instability and its relation to phonon instability in a number of materials. Besides classic cases of bcc-Ti, Hf and Zr, authors have discussed other cases as well.…”

“…7,[32][33][34][35][36][37][38][39][40][41][42] To the best of our knowledge, all first-principles calculations have been carried out only for Fe 3 C, and a very few attempts have been made to predict its stability and understand mechanical properties of multi-component cementite. Only recently, Jang et al 40 reported the effect of Si on the stability of Fe 3 C. The crystal structure of cementite, Fe 3 C, is well established.…”

Effect of interlamellar spacing on the elastoplastic behavior of C70 pearlitic steel: Experimental results and self-consistent modeling

“…Random orientations distribution of lattice in ferritic grains was assumed. In the case of cementite only theoretical (ab initio calculation) tensor of single crystal elastic constants (C ij ) is available [31]. However, the theoretical data (averaged for polycrystalline aggregate) does not agree with experimentally determined Young's modulus (E) and Poison's ratio (m) [32,33].…”

First-Principles Calculations on Stabilization of Iron Carbides (Fe3C, Fe5C2, and η-Fe2C) in Steels by Common Alloying Elements

“…Electronic, structural, and magnetic properties of pure cementite were described in many previous communications. [7,[10][11][12] Furthermore, there are detailed studies of thermodynamic properties of pure cementite, [9,13] elastic properties, [14][15][16][17] point defects, and possible C diffusion paths. [12] The energetics and electronic structure of impurity substituted cementite have also been the focus of a considerable number of previous studies.…”