Re: [SIESTA-L] Overestimation of optimized lattice constant for SmTe
On 03/05/2008, at 12:39, Nidhi Sharma wrote: Hi to all, I am trying to compute the energy for different lattice constant to get the E vs V graph (in B1 phase of Smte using LDA). For this I have selected the range from 5.5 to 7.5 Ang in steps of 0.05. After Murnaghan fit optimize lattice consatnt comes out to be 6.87 Ang (Expt =6.594 Ang) and bulk modulus 38.3 GPa. (Expt = 40 GPa). I have also changed the different step size and the range but every time the optimized lattice constant is overestimated. Is it worth using this data for calculation ? Is it possible that some times lattice constant overestimates the experimental value ? Yes, definitively is possible! If I were you I would check with another basis set (smaller eshift, different split norm) and with a GGA functional. Regards, Eduardo If not then please guide us where I am wrong ? Regards, Nidhi Best Jokes, Best Friends, Best Food. Get all this and more on Best of Yahoo! Groups.smte.fdf
Re: [SIESTA-L] Overestimation of optimized lattice constant for SmTe
I would say that for LDA overestimation of lattice constant is not OK. (Although I cannot guarantee that this is the case for SmTe) Normally, LDA lattice constant should be 1% smaller than expt, while in GGA up to 2% overestimation is OK. Otherwise, try other set of parameters.
Re: [SIESTA-L] Overestimation of optimized lattice constant for SmTe
It does not matter with step you use to plot this ExV surface, the result must be the same if you are using the same basis set and so on ... by the way, 4% isent so bad result for a first guess basis, and your Bulk modulus is absolutelly ok ... another think is, try to compare your results with another DFT results instead to experimental values only, some times DFT dosent agree so well with the experiments... On Sat, May 3, 2008 at 12:39 PM, Nidhi Sharma [EMAIL PROTECTED] wrote: Hi to all, I am trying to compute the energy for different lattice constant to get the E vs V graph (in B1 phase of Smte using LDA). For this I have selected the range from 5.5 to 7.5 Ang in steps of 0.05. After Murnaghan fit optimize lattice consatnt comes out to be 6.87 Ang (Expt =6.594 Ang) and bulk modulus 38.3 GPa. (Expt = 40 GPa). I have also changed the different step size and the range but every time the optimized lattice constant is overestimated. Is it worth using this data for calculation ? Is it possible that some times lattice constant overestimates the experimental value ? If not then please guide us where I am wrong ? Regards, Nidhi -- Best Jokes, Best Friends, Best Food. Get all this and more on Best of Yahoo! Groups.http://in.rd.yahoo.com/tagline_groups_11/*http://in.promos.yahoo.com/groups/bestofyahoo/
