To All responding to my initial thread: I'm amazed and encouraged by the response of the community to my problem. I will be trying your suggestions...e.g., a "rich man's" Wannier projection. Of course, this trapping into a "metastable state" is typical of many highly nonlinear systems of any type...such as the many body nonlinear Navier-Stokes equations, sometimes referred to as the "weather."
Someone pointed out the importance of covalency in the Cu-O double bond, and I'm not sure how to accommodate this in PWscf (in the simple Hubbard Hamiltonian, you just futz around with U and t in a Monte Carlo simulation...in 1 or 2 dimensions). As I mentioned in my original posting, there may be a profound issue here that DFT LDA+U may find difficult to address...it's probably the origin of HTSC. There is a polemic published back in 1989 by Phil Anderson to the effect that pseudopotential theory may not apply to divalent Cu-O bonds. Nonetheless, I would still like to find a way to get a Hubbard Gap in divalent CuO from a PW/PP starting point. I'm old enough to remember this was once quite a task for NiO. Paul M. Grant, PhD Principal, W2AGZ Technologies Visiting Scholar, Applied Physics, Stanford University EPRI Science Fellow (Retired) IBM Research Staff Member Emeritus w2agz at pacbell.net http://www.w2agz.com ? ? -----Original Message----- From: pw_forum-bounces at pwscf.org [mailto:pw_forum-boun...@pwscf.org] On Behalf Of Agostino Migliore Sent: Thursday, December 13, 2007 10:01 PM To: PWSCF Forum Subject: Re: [Pw_forum] CuO, LDA+U, Pseudopots, etc. Yes, I know. By saying "convergence problem" I just meant, in this specific case, that the scf calculation does not reach the right minimum (i.e., the lowest one), but get trapped into some another (local) minimum. As to your second point, I will send you a further email in a short time. Thank you Agostino > > > Dear Agostino, > > if the calculation did converge to a local minimum, it means that the > system has more than one minimum, not that there is a convergence > problem (of course, the convergence strategy you choose will affect > the minimum in which you fall). > > It would be very interesting to know more (when you have time) about > these minima - e.g. what were the projections of the minority spin > in the two cases. > > Thanks ! > > nicola _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
