First-principles calculations on the structural, electronic, magnetic, and elastic properties of (Fe, Cr)23C6

The first-principles calculations were used to comprehensively assess the structural, electronic, magnetic, and elastic properties of Fe23−xCrxC6 (x = 0–23). The absolute temperature stability follows the sequence of Fe1Cr22C6 (Fe: 4a) > Fe3Cr20C6 (Fe: 4a, 8c) > Fe15Cr8C6 (Fe: 4a, 8c, 48h) > Fe23C6 (Fe: 4a, 8c, 32f, 48h). There is a coexistence of covalent, ionic, and metallic bonds in Fe23C6, Fe15Cr8C6, Fe3Cr20C6, Fe1Cr22C6, and Cr23C6 according to the electronic analysis. In addition, the iron content of 0.4 triggers the magnetic transition, suggesting that a critical point exists between the paramagnetic nature and ferromagnetism. Around the concentration of x = 0.5, the longer nearest neighbor length of Fe–C corresponds to the higher value of magnetic moment. Up to the iron content of 1.0, Fe23C6 carbides give rise to an extraordinary magnetic property. The composition and Wyckoff position collectively determines the mechanical properties. Except for the hardness, the mechanical property improves with increasing chromium concentrations. Furthermore, the compounds Fe23−xCrxC6 (x = 0, 9, 10, 11) are brittle. The present work enriches the pool of information that is necessary for the design and property control of Fe-based materials.