Dear Padmaja Patnaik There are several things wrong or at least approximative in your reasoning.
-First your estimation of J_0 is quite crude at least for itinerant magnetism. A better estimate of J_0 would require a spin spiral calculation (not available within pwscf) and then a fit with Heisenberg model. -Second you only include first neighbors while it is well known that next nearest neighbors are very important especially for Iron. -last but not least: your estimation of T_c is based on mean field approximation which is known to overestimate the transition temperature.. Cyrille -- ============================================================== Cyrille Barreteau phone : +33 (0)1 69 08 29 51 CEA Saclay fax : +33 (0)1 69 08 84 46 IRAMIS, SPCSI, B?timent 462 email cyrille.barreteau at cea.fr 91191 Gif sur Yvette Cedex FRANCE ~~~~~~~~~~~~~~~~~~~~~~~~ home page: http://iramis.cea.fr/Pisp/cyrille.barreteau/ Lab page: http://iramis.cea.fr/spcsi/ ============================================================= On Tue, 2011-03-22 at 04:57 +0000, Padmaja Patnaik wrote: > Hi > > I am calculating the Curie Temperature for Iron. The experimental > value for this is 1043 K. I am getting the value as 2398.97 K. I am > using the following way to calculate. > Find out the ferromagnetic and anti-ferromagnetic energy of Fe. The > difference between these two gives the value of J_0. Then, > T_c = [2/3] [J_0/K_B] > > Please suggest me what is wrong? Why am I getting such a high value. > On the other hand I am getting very low value for Ni, whose > experimental Curie temperature is 627K and I am getting 315K. > Thanking you in advance, > regards > Padmaja Patnaik > Research Scholar > Dept of Physics > IIT Bombay > Mumbai, India > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum
