[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
Now read Martins mail again, and consider what he writes about enlarging the lattice constants (i.e. increasing the volume of the cell). Then, ponder what it means that you have 2 degrees of freedom here: a and c, or alternatively, volume and c/a. Stefaan Ghosh SUDDHASATTWA wrote: Dear Martin, Probably I am responding to your mail after a long time. And moreover, you are absolutely correct. If Pu is imagined to be in the Zr atomic positions, it is very natural that the occupation of Pu would naturally increase the c/a ratio and there is no meaning to do a structure optimization for cases like -2 % or -5 % change in c/a ratio. The equilibrium c/a would be somewhere around +12-15 % change (gross) and this is what is expected from physics. That is what I get from Wien2k Thanks Stefaan and Martin, Suddhasattwa Ghosh -Original Message- From: wien-bounces at zeus.theochem.tuwien.ac.at [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Martin Pieper Sent: Tuesday, March 02, 2010 6:32 PM To: A Mailing list for WIEN2k users Subject: Re: [Wien] [Wien2k Users] Lattice Stability using StructureOptimization Dear Ghosh Suddhasattwa, being a beginner with Wien2k myself and not having read your exchange with Stefaan I probably should be quiet to avoid confusion but maybe its simple: Did you adapt (enlargen) the lattice constant when you put in Pu instead of Zr? I would expect that Pu needs a lot more space than Zr and, therefore, you might simply be too far away from any reasonable lattice constant and far out of the trial range of the optimization procedure... Best regards, Martin Am Montag, 8. M?rz 2010 schrieb Ghosh SUDDHASATTWA: Dear Dr.Stefaan, Coming back to the problem we discussed regarding lattice stability a few days back, I have done a few things but am not able to proceed further. I imagine Pu in a Zr lattice (hcp, space group 194) There is only one equivalent position (0.333 0.67 0.25) I replaced Zr atom with the Pu atom. My approach was the following 1. Calculate ENE without spin orbit and with spin orbit 2. Structure optimization (Option 5) The ENE without spin orbit was -118767.962 Ry and with spin orbit was -118769.097 Ry. I chose Option 5 for the structure optimization and it created 16 different struct files. Optimize.job was run and it did not give any errors. (Removed # from x dstart only) When I chose energy vs volume in plot; it gave a linear variation and not like what is given in the UG guide for TiC. Can you please tell me if I have done any mistake? Suddhasattwa Ghosh -- Stefaan Cottenier Center for Molecular Modeling (CMM) Ghent University Technologiepark 903 (2nd floor) BE-9052 Zwijnaarde Belgium http://molmod.Ugent.be email: Stefaan . Cottenier /at/ UGent . be
[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
Dear Stefaan, Probably you are right. But then how to tackle with the point you raised (point no.2) One thing would be to vary c/a with constant volume (option 2), but then I do not have a priori information on the optimized parameters. Suddhasattwa Ghosh -Original Message- From: wien-boun...@zeus.theochem.tuwien.ac.at [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Stefaan Cottenier Sent: Monday, March 08, 2010 7:53 PM To: A Mailing list for WIEN2k users Subject: Re: [Wien] [Wien2k Users] Lattice Stability using StructureOptimization 1) I hope you know what you are plotting if you make a 2D (a,c) scan and then chose energy vs volume in plot. 2) Think about this: a section of a parabola far away from its minimum might look like a straight line. Stefaan Coming back to the problem we discussed regarding lattice stability a few days back, I have done a few things but am not able to proceed further. I imagine Pu in a Zr lattice (hcp, space group 194) There is only one equivalent position (0.333 0.67 0.25) I replaced Zr atom with the Pu atom. My approach was the following 1. Calculate ENE without spin orbit and with spin orbit 2. Structure optimization (Option 5) The ENE without spin orbit was -118767.962 Ry and with spin orbit was -118769.097 Ry. I chose Option 5 for the structure optimization and it created 16 different struct files. Optimize.job was run and it did not give any errors. (Removed # from x dstart only) When I chose energy vs volume in plot; it gave a linear variation and not like what is given in the UG guide for TiC. Can you please tell me if I have done any mistake? Suddhasattwa Ghosh ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Stefaan Cottenier Center for Molecular Modeling (CMM) Ghent University Technologiepark 903 (2nd floor) BE-9052 Zwijnaarde Belgium http://molmod.Ugent.be email: Stefaan . Cottenier /at/ UGent . be ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
But then how to tackle with the point you raised (point no.2) One thing would be to vary c/a with constant volume (option 2), but then I do not have a priori information on the optimized parameters. So what? The total energy tells you in which direction you have to change the volume (smaller or larger). Keep on going, until you find the minimum. Stefaan
[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
Dear Dr.Stefaan, Coming back to the problem we discussed regarding lattice stability a few days back, I have done a few things but am not able to proceed further. I imagine Pu in a Zr lattice (hcp, space group 194) There is only one equivalent position (0.333 0.67 0.25) I replaced Zr atom with the Pu atom. My approach was the following 1. Calculate ENE without spin orbit and with spin orbit 2. Structure optimization (Option 5) The ENE without spin orbit was -118767.962 Ry and with spin orbit was -118769.097 Ry. I chose Option 5 for the structure optimization and it created 16 different struct files. Optimize.job was run and it did not give any errors. (Removed # from x dstart only) When I chose energy vs volume in plot; it gave a linear variation and not like what is given in the UG guide for TiC. Can you please tell me if I have done any mistake? Suddhasattwa Ghosh -- next part -- An HTML attachment was scrubbed... URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20100308/d0729353/attachment.htm
[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
1) I hope you know what you are plotting if you make a 2D (a,c) scan and then chose energy vs volume in plot. 2) Think about this: a section of a parabola far away from its minimum might look like a straight line. Stefaan Coming back to the problem we discussed regarding lattice stability a few days back, I have done a few things but am not able to proceed further. I imagine Pu in a Zr lattice (hcp, space group 194) There is only one equivalent position (0.333 0.67 0.25) I replaced Zr atom with the Pu atom. My approach was the following 1. Calculate ENE without spin orbit and with spin orbit 2. Structure optimization (Option 5) The ENE without spin orbit was -118767.962 Ry and with spin orbit was -118769.097 Ry. I chose Option 5 for the structure optimization and it created 16 different struct files. Optimize.job was run and it did not give any errors. (Removed # from x dstart only) When I chose energy vs volume in plot; it gave a linear variation and not like what is given in the UG guide for TiC. Can you please tell me if I have done any mistake? Suddhasattwa Ghosh ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Stefaan Cottenier Center for Molecular Modeling (CMM) Ghent University Technologiepark 903 (2nd floor) BE-9052 Zwijnaarde Belgium http://molmod.Ugent.be email: Stefaan . Cottenier /at/ UGent . be
[Wien] [Wien2k Users] Lattice Stability using Structure Optimization
Dear Ghosh Suddhasattwa, being a beginner with Wien2k myself and not having read your exchange with Stefaan I probably should be quiet to avoid confusion but maybe its simple: Did you adapt (enlargen) the lattice constant when you put in Pu instead of Zr? I would expect that Pu needs a lot more space than Zr and, therefore, you might simply be too far away from any reasonable lattice constant and far out of the trial range of the optimization procedure... Best regards, Martin Am Montag, 8. M?rz 2010 schrieb Ghosh SUDDHASATTWA: Dear Dr.Stefaan, Coming back to the problem we discussed regarding lattice stability a few days back, I have done a few things but am not able to proceed further. I imagine Pu in a Zr lattice (hcp, space group 194) There is only one equivalent position (0.333 0.67 0.25) I replaced Zr atom with the Pu atom. My approach was the following 1.Calculate ENE without spin orbit and with spin orbit 2.Structure optimization (Option 5) The ENE without spin orbit was -118767.962 Ry and with spin orbit was -118769.097 Ry. I chose Option 5 for the structure optimization and it created 16 different struct files. Optimize.job was run and it did not give any errors. (Removed # from x dstart only) When I chose energy vs volume in plot; it gave a linear variation and not like what is given in the UG guide for TiC. Can you please tell me if I have done any mistake? Suddhasattwa Ghosh -- Dr. Martin W. Pieper Institut f. Physik, Karl-Franzens Universit?t Graz Universit?tsplatz 5, A - 8010 Graz, AUSTRIA Tel.: +43-316-380-8564, Fax: +43-316-380-9816, email: martin.pieper at ifp.tuwien.ac.at
