Comparative study between LMTO and FPLAPW into the calculation of the electronic structure of carbide Cr23C6

Considering the actual state of the art in Materials Science, it is necessary to do a theoretical analysis of the compounds obtained through experimenting, with the objective of understanding them better, by foreseeing their behaviour and possible new compounds. For this, in this work, we calculate electronic structures of Cr23C6 chromium carbide, which are present in fast steels, using two methods of calculating the band structure of first principles, the method of linear muffin-tin orbital (LMTO) with the Andersen's atomic sphere approximation (ASA) and the method of linear plain and expanded waves (LAPW) with generalized gradient approximation (GGA). Through calculations of formation energy in relation to its volume we obtain the equilibrium volume of 379.16 u.a. using the LMTO, and 375.13 u.a, using the LAPW. In the equilibrium volume we calculated some fundamental state properties. We observed an extremely low magnetization in both methods; nevertheless, in LAPW we verified a little magnetic moment in the Cri site that is 0.2512 mu(B). The method LAPW affirms the existence of an interstitial region motivating the charge transference to this region. As the LMTO does not have the interstitial region, we do not see the charge transference to this region; in this case the charges come out of the C and Cr1 sites to take place in the Cr11 site. The density of states (DOS) shows that there is an interaction between the "s" states of C with the other sites and in a more intense way with the Cr11 site. When we compared the DOS, in relation to the methods used, we saw that in case of the LMTO, these are slightly placed in regions where energy is lower as well as its Fermi energy. (c) 2006 Elsevier B.V. All rights reserved.