TBLITE_MIXER
Controls tblite’s modified Broyden SCC-variable mixer when SCC_MIXER is set to TBLITE, either explicitly or through AUTO where AUTO selects tblite. The mixer variables are the self-consistent xTB/DFTB populations and, for methods that require them, atomic multipoles. ITERATIONS limits the number of tblite SCC-mixer updates, while MEMORY controls how many previous Broyden update vectors are retained. These are independent quantities when MEMORY is set explicitly; otherwise MEMORY follows ITERATIONS, matching the tblite library default. DAMPING controls the size of the retained population/multipole update. OMEGA0, MIN_WEIGHT, MAX_WEIGHT, and WEIGHT_FACTOR expose tblite’s modified-Broyden weighting constants. ITERATIONS is the tblite-side SCC-mixer update limit and defaults to the native tblite value of 250. When SCC_MIXER is explicitly set to TBLITE, CP2K also sets the regular DFT/SCF/MAX_SCF limit to ITERATIONS so that the tblite SCC cycle is not truncated by CP2K’s default SCF limit. With SCC_MIXER AUTO or CP2K, DFT/SCF/MAX_SCF keeps its normal CP2K meaning. This section configures the tblite SCC mixer, not the regular CP2K charge mixer. With SCC_MIXER CP2K, the CP2K-side SCC-variable mixer is controlled by DFT/SCF/MIXING. With QS/LS_SCF, this section is ignored and CP2K resets SCC_MIXER to NONE internally, because LS_SCF performs the density-matrix optimization instead of a separate SCC-variable mixing step. Native tblite REFERENCE_CLI diagnostics inherit this section. ITERATIONS and SOLVER are representable by tblite run directly; CP2K reports inherited MEMORY, DAMPING, or Broyden-weight settings that native tblite CLI cannot reproduce. [Edit on GitHub]
Keywords
Keyword descriptions
- DAMPING
Type: real
Default: 4.00000000E-001
Usage: DAMPING 0.4Description: Damping parameter for the tblite modified Broyden SCC mixer. It controls the size of the population/multipole update retained by the native tblite mixer between SCC iterations. Smaller values damp oscillatory SCC cycles more strongly but may slow convergence; larger values can accelerate well-behaved cases but may destabilize difficult ones. For CP2K-internal GFN1-xTB UKS k-point calculations with explicit SCC_MIXER TBLITE, CP2K uses a conservative damping of 0.25 unless DAMPING is set explicitly.
- ITERATIONS
Type: integer
Default: 250
Usage: ITERATIONS 250Description: Maximum number of tblite SCC-mixer updates. This is the tblite-side SCC iteration limit, matching native tblite’s –iterations setting for reference CLI diagnostics. For explicit SCC_MIXER TBLITE runs, CP2K synchronizes DFT/SCF/MAX_SCF to this value. For SCC_MIXER AUTO or CP2K, DFT/SCF/MAX_SCF remains the normal CP2K SCF-loop iteration limit. ITERATIONS is independent of MEMORY, which controls the Broyden history length.
- MAX_WEIGHT
Type: real
Default: 1.00000000E+005
Usage: MAX_WEIGHT 100000.0Description: Upper bound for the dynamic Broyden history weight derived from the current SCC residual. The default matches native tblite and caps the influence of very small residual norms.
- MEMORY
Type: integer
Default: 0
Usage: MEMORY 250Description: Number of previous modified-Broyden update vectors kept by the tblite SCC mixer. This is a history length, not an iteration limit. Larger values retain more history and use more memory; smaller values reduce the history and can be more robust for difficult SCC cycles. A value of zero means library default: inherit ITERATIONS, as native tblite does when it constructs the Broyden mixer from calc%max_iter.
- MIN_WEIGHT
Type: real
Default: 1.00000000E+000
Usage: MIN_WEIGHT 1.0Description: Lower bound for the dynamic Broyden history weight derived from the current SCC residual. The default matches native tblite and prevents tiny weights from removing history vectors from the update.
- OMEGA0
Type: real
Default: 1.00000000E-002
Usage: OMEGA0 0.01Description: Regularization weight added to the diagonal of tblite’s modified-Broyden linear system. The default matches the hard-coded value in native tblite and damps nearly singular history updates without changing the first simple-damping step.
- SOLVER
Type: enum
Default: GVD
Usage: SOLVER (GVD|GVR)Description: Electronic eigensolver selected for native tblite SCC calculations where tblite owns the electronic solve, and forwarded to native REFERENCE_CLI diagnostics as tblite run –solver. GVD is tblite’s default LAPACK divide-and-conquer generalized symmetric eigensolver. GVR selects LAPACK’s relatively robust generalized symmetric eigensolver. Production CP2K/tblite calculations still use CP2K’s electronic diagonalization machinery.
Valid values:
GVDUse LAPACK’s divide-and-conquer generalized symmetric eigensolver.GVRUse LAPACK’s relatively robust generalized symmetric eigensolver.
- WEIGHT_FACTOR
Type: real
Default: 1.00000000E-002
Usage: WEIGHT_FACTOR 0.01Description: Residual-to-weight scaling factor used by tblite’s modified Broyden mixer. For a residual norm above WEIGHT_FACTOR/MAX_WEIGHT, the dynamic weight is approximately WEIGHT_FACTOR divided by that residual norm; otherwise MAX_WEIGHT is used before applying MIN_WEIGHT. The default matches native tblite.