Feature: add gga_grad parameter for noncollinear spin GGA functional - #7758
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dyzheng wants to merge 7 commits into
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Feature: add gga_grad parameter for noncollinear spin GGA functional#7758dyzheng wants to merge 7 commits into
dyzheng wants to merge 7 commits into
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August 2, 2026 11:06
The gga_grad=3 path (default for nspin=4) incorrectly used the collinear approximation (gga_grad=1) within libxc instead of the Scalmani-Frisch gradient method (gga_grad=2). This caused inconsistent results for noncollinear GGA calculations. Fix: extend libxc_pot.cpp and libxc_tools.cpp gga_grad==2 checks to also match gga_grad==3, routing both through the SF gradient path. Also fix input_parameter.h: restore out_hsr/out_hsk/out_hsr_npz_compat members removed during cherry-pick that were present in newer develop.
- Fix libxc_tools.cpp vtxc: use chr->rho[is][ir] (nspin=4 density) instead of libxc-format rho (up/dn spin density) - Revert libxc_setup.cpp to develop (the accel branch changes had map key collision, PBEH param count error, and weakened param validation) - Revert input_parameter.h: restore develop defaults for device, sc_* params, xc_exch_ext/xc_corr_ext; keep only gga_grad=3 - Revert docs to develop version
- libxc_pot.cpp: comments for SF gradient decomposition, gga_grad branching - libxc_tools.cpp: comment for nspin=4 SF dh path with 4-component potential - xc_pot.cpp: comment for non-libxc SF builtin dispatch - xc_functional_gga_noncol_sf_builtin.cpp: header comment block with Scalmani-Frisch reference, chain-rule formulas, and step-by-step labels
mohanchen
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Feature Discussed
…ain.md Add item.description for gga_grad in read_input_item_elec_stru.cpp and regenerate docs/parameters.yaml to fix the CI check that compares the yaml against the output of --generate-parameters-yaml. Also add the gga_grad entry to docs/advanced/input_files/input-main.md.
…thm (gga_grad=0) - Add gga_grad parameter to XC_Functional::v_xc and XC_Functional_Libxc::v_xc_libxc instead of reading PARAM.inp.gga_grad inside the xc module; update all call sites. - Pass use_sf/has_mag down to convert_vtxc_v, convert_v_nspin4 and convert_v_nspin4_sf; drop PARAM reads from libxc_pot.cpp, libxc_tools.cpp, xc_pot.cpp and the SF builtin (net global-dependency delta of the PR is now zero). - gga_grad=0 (new default) selects the original algorithm so existing results are unchanged; gga_grad=1 keeps the collinear approximation, 2/3 select the SF-based paths. - Revert unrelated default arguments added to libxc_abacus.h interfaces and restore the init_func doc comment. - Forward-declare Charge in xc_functional_gga_noncol_sf_builtin.h.
…_vtxc_v The gga_grad=2/3 branch of convert_vtxc_v wrote the 4-component dh into v(2,:) and v(3,:) of a 2-row matrix (out-of-bounds). Map dh back to the spin-up/down representation with the inverse of the SF decomposition: v_up -= dh0 + sum_mu dh_mu * m_hat_mu, v_dn -= dh0 - sum_mu dh_mu * m_hat_mu. The vtxc accumulation over the 4 nspin=4 channels is unchanged.
Methods 2 and 3 share the same chain-rule spin-up/down gradients grad(rho_up/dn) = (grad(rho) +/- m_hat . grad(m))/2, but differ in the divergence of h = df/d(grad rho) in the potential: - gga_grad=2 (projected): v_mu -= m_hat_mu * div((h_up - h_dn)/2), dropping the (h_up - h_dn) . grad(m_hat_mu) cross terms; - gga_grad=3 (full SF): v_mu -= div((h_up - h_dn)/2 * m_hat_mu), retaining all cross terms. Implement the projected variant in cal_dh_sf (LIBXC path) and in v_xc_ncgga_sf_builtin (built-in path, now also dispatched for gga_grad=2), and document the formula-level differences in the code comments and in the gga_grad INPUT documentation.
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AGENTS.mdanddocs/developers_guide/agent_governance.md.source/changes.Linked Issue
Fix #7730
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