From owner-chemistry@ccl.net Sun Jul 2 10:50:00 2017 From: "Andrew Scott Rosen rosen^u.northwestern.edu" To: CCL Subject: CCL:G: Unrestricted vs. restricted DFT for closed-shell metal complex Message-Id: <-52866-170702005700-21202-tkhyhQDSe/8dvY8UTYIxkA|-|server.ccl.net> X-Original-From: "Andrew Scott Rosen" Date: Sun, 2 Jul 2017 00:56:59 -0400 Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu] Hello, I have a question regarding the choice of unrestricted versus restricted calculations in DFT. Let's say that I am dealing with a Cu(I) organometallic complex that I anticipate would have a spin multiplicity of 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this complex. Under this assumption, the system is not open-shell. As such, it seems that a restricted calculation would be most appropriate. Would there be any benefit in running an unrestricted calculation (still as a singlet) in this case? Additionally, what would an unrestricted calculation on a system that's a singlet even mean, especially if I don't use specific keywords (e.g. in Gaussian) to try and obtain a broken- symmetry state? To provide context, I ask because I start with a Cu(II) complex that reduces to a Cu(I) complex. I do an unrestricted calculation when modeling the Cu(II) complex, and I want to compute the energy of the resulting Cu(I) complex for comparison. Thank you greatly for any input. Best regards, Andrew