Hello all,
I am computing the tight-binding (TB) Hamiltonian of a monolayer MoS₂ (1×1 unit cell with three atoms) using Quantum ESPRESSO + Wannier90. I'm using d orbitals for Mo and p orbitals for S atoms. Here is a snippet of my wannier90 settings: ``` num_iter = 0 dis_num_iter = 0 … wannier_plot = True … begin projections Mo:d:z=0,0,1:x=1,0,0 S:l=1,mr=2:z=0,0,1:x=1,0,0 S:l=1,mr=3:z=0,0,1:x=1,0,0 S:l=1,mr=1:z=0,0,1:x=1,0,0 end projections ``` Please note that I have set num_iter =0 because I want to preserve wannier function shape as typical orbital (px py pz dxy …) This configuration enforces the order of the p_x, p_y, p_z orbitals (Actually its p_x, p_x, p_y, p_y, p_z, p_z for two S atoms) . I expected this setup to generate the y-axis as (0,1,0). Using wannier90 result, I’m analyzing the p–p Hamiltonian matrix (3×3) for two S atoms aligned along the x-axis (let’s call this H_deg0) and after a 60° rotation about the z-axis (H_deg60). I applied the rotation using the operator D(R), where R is the 60° rotation matrix around the z-axis. Although the absolute values of the rotated Hamiltonian match those of H_deg60, some components (off diagonal terms) show opposite signs, which was unexpected. This discrepancy suggests that the directions of the p_x, p_y, and p_z orbitals used in Wannier90 may not align with the conventional (x, y, z) coordinate system. I also have visualized the Wannier functions via .xsf files, it seems that the p_y orbital has an opposite sign: the yellow lobes for -y direction and blue lobes for +y direction. This probably suggests that p_y orbital used in Wannier90 has an opposite sign, generating left-handed coordinate. In summary, my main questions are: 1. Could someone explain how Wannier90 determines the sign and orientation of wannier function? 2. Is there a way to constrain the positions of Wannier functions at the center of each atom and enforce their shapes to resemble standard atomic orbitals (e.g., p_x, p_y, p_z, d_z^2, etc.)— to use Wannier90 like LCAO. Best regards, ------------------ Moon-ki Choi, Ph.D. Postdoctoral researcher Material Research Laboratory, University of Illinois Urbana-Champaign 612-229-9732 Personal website: https://sites.google.com/view/moonkichoi/
_______________________________________________ Wannier mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/wannier
