Dear QE-users/Developers,
Hi. I am trying to do an SCF calculation on a system with AFM order in z-direction with a metallic impurity atom in the unit cell. I am employing the simplest version of DFT+U (lda_plus_u_kind=0) and QE-6.7. The values of Hubbard_U is set to some non-zero value for the spin-up and spin-down atoms. It is seen from the eigenvalues after iteration #1: ------------------------------------------ atom 1 Tr[ns(na)] (up, down, total) = 0.67656 0.33866 1.01522 spin 1 eigenvalues: 0.057 0.060 0.060 0.111 0.111 0.116 0.162 spin 2 eigenvalues: 0.037 0.037 0.039 0.041 0.041 0.044 0.101 atom 2 Tr[ns(na)] (up, down, total) = 0.38044 2.32226 2.70270 spin 1 eigenvalues: 0.033 0.033 0.035 0.053 0.058 0.077 0.093 spin 2 eigenvalues: 0.091 0.121 0.126 0.191 0.372 0.656 0.766 ------------------------------------------ that we should have (?) total number of 3x5=15 metastable states. To discover the properties of those states, I used the following 15 different combinations of "starting_ns_eigenvalues": ---------------------------- starting_ns_eigenvalue(3,2,1)=1.0, starting_ns_eigenvalue(3,1,2)=1.0 starting_ns_eigenvalue(3,2,1)=1.0, starting_ns_eigenvalue(4,1,2)=1.0 starting_ns_eigenvalue(3,2,1)=1.0, starting_ns_eigenvalue(5,1,2)=1.0 starting_ns_eigenvalue(3,2,1)=1.0, starting_ns_eigenvalue(6,1,2)=1.0 starting_ns_eigenvalue(3,2,1)=1.0, starting_ns_eigenvalue(7,1,2)=1.0 starting_ns_eigenvalue(6,2,1)=1.0, starting_ns_eigenvalue(3,1,2)=1.0 starting_ns_eigenvalue(6,2,1)=1.0, starting_ns_eigenvalue(4,1,2)=1.0 starting_ns_eigenvalue(6,2,1)=1.0, starting_ns_eigenvalue(5,1,2)=1.0 starting_ns_eigenvalue(6,2,1)=1.0, starting_ns_eigenvalue(6,1,2)=1.0 starting_ns_eigenvalue(6,2,1)=1.0, starting_ns_eigenvalue(7,1,2)=1.0 starting_ns_eigenvalue(7,2,1)=1.0, starting_ns_eigenvalue(3,1,2)=1.0 starting_ns_eigenvalue(7,2,1)=1.0, starting_ns_eigenvalue(4,1,2)=1.0 starting_ns_eigenvalue(7,2,1)=1.0, starting_ns_eigenvalue(5,1,2)=1.0 starting_ns_eigenvalue(7,2,1)=1.0, starting_ns_eigenvalue(6,1,2)=1.0 starting_ns_eigenvalue(7,2,1)=1.0, starting_ns_eigenvalue(7,1,2)=1.0 --------------------------------------- and performed the 15 scf calculations. Surprisingly, I got the same results for the total energies for all 15 different inputs: ------------------------------ ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ! total energy = -879.68389676 Ry ------------------------------------------- On the other hand, the convergency has been achieved with different numbers of iterations: ----------------------------- convergence has been achieved in 70 iterations convergence has been achieved in 58 iterations convergence has been achieved in 48 iterations convergence has been achieved in 67 iterations convergence has been achieved in 57 iterations convergence has been achieved in 65 iterations convergence has been achieved in 52 iterations convergence has been achieved in 72 iterations convergence has been achieved in 59 iterations convergence has been achieved in 48 iterations convergence has been achieved in 54 iterations convergence has been achieved in 57 iterations convergence has been achieved in 46 iterations convergence has been achieved in 70 iterations convergence has been achieved in 62 iterations --------------------------------------- Now question arises: 1- If the total energies are the same, maybe the QE code, irrespective of the starting_ns_eigenvalues, leads the system to global-minimum (or specific state) state ? 2- Why the number of convergency iterations differ? Any comments is highly appreciated. With kind regards, Mahmoud Payami AEOI, Tehran, Iran Email: mpay...@aeoi.org.ir Phone: +98 (0)21 82066504
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