Dear All, I finished an optimisation for 225 space group with -15% to 25% volume change.
If I plot the optimization cure for different vol parameters, I see the shape of ENE vs. Vol curve changes and the optimised lattice parametes also changes (at third digit). If I plot the curve for -15 to 25% then I get the below curve *https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/ <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/>*1.ps <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> and the optimised lattice parameters are 21.1924 bohr = 11.2145 Ang For -10 to 25%, <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/2.ps> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/2.ps <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> 21.1984 bohr = 11.2177 Ang For -5 to 25% <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/3.ps> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/3.ps <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> 21.1915 bohr = 11.2140 Ang 0.0 to 25 % <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/4.ps> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/4.ps <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> 21.1917 bohr = 11.2141 Ang for 5.0 to 25 % https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/5.ps <https://sites.google.com/site/dftfatima5/letter/mailing-list-queries?pli=1/1.ps> 21.2026 bohr = 11.2199 Ang My query is: 1. Why the optimised lattice parameters are changing if we select different set of data points? The ground state should be same in all cases. Is it? 2. We see from the lattice parameter the change is at third order, can we take any lattice parameters (a0)? How much the third digit changes the electronic properties? Warm regards Fatima
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