Section OT

• Sets the various options for the orbital transformation (OT) method. Default settings already provide an efficient, yet robust method. Most systems benefit from using the FULL_ALL preconditioner combined with a small value (0.001) of ENERGY_GAP.Well-behaved systems might benefit from using a DIIS minimizer.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / SCF / DIAGONALIZATION / OT

• This section cannot be repeated and can be optional.

• This section cites the following references: [VandeVondele2003] [Weber2008]

• Subsections

  • none

• Keywords

  • SECTION_PARAMETERS
  • ALGORITHM
  • BROYDEN_BETA
  • BROYDEN_GAMMA
  • BROYDEN_SIGMA
  • ENERGIES
  • ENERGY_GAP
  • EPS_IRAC
  • EPS_IRAC_FILTER_MATRIX
  • EPS_IRAC_QUICK_EXIT
  • EPS_IRAC_SWITCH
  • EPS_TAYLOR
  • GOLD_TARGET
  • IRAC_DEGREE
  • LINESEARCH
  • MAX_IRAC
  • MAX_TAYLOR
  • MINIMIZER
  • MIXED_PRECISION
  • NONDIAG_ENERGY
  • NONDIAG_ENERGY_STRENGTH
  • N_HISTORY_VEC
  • OCCUPATION_PRECONDITIONER
  • ON_THE_FLY_LOC
  • ORTHO_IRAC
  • PRECONDITIONER
  • PRECOND_SOLVER
  • ROTATION
  • SAFE_DIIS
  • SCP_DFT
  • SCP_NDDO
  • STEPSIZE

• Keyword descriptions

  SECTION_PARAMETERS
  	&OT T
  	controls the activation of the ot method
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ALGORITHM
  	ALGORITHM STRICT
  	Algorithm to be used for OT
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: STRICT
  	List of valid keywords: IRAC Orbital Transformation based Iterative Refinement of the Approximative Congruence transformation (OT/IR). STRICT Strict orthogonality: Taylor or diagonalization based algorithm.
  	This keyword cites the following references: [VandeVondele2003] [VandeVondele2005] [Weber2008]

  BROYDEN_BETA
  	BROYDEN_BETA 0.9
  	Underrelaxation for the broyden mixer
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 9.00000000E-01

  BROYDEN_GAMMA
  	BROYDEN_GAMMA 0.5
  	Backtracking parameter
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-01

  BROYDEN_SIGMA
  	BROYDEN_SIGMA 0.7
  	Dampening parameter.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 7.00000000E-01

  ENERGIES
  	ENERGIES
  	Optimize orbital energies for use in Fermi-Dirac smearing (requires ROTATION and FD smearing to be active).
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ENERGY_GAP
  	ENERGY_GAP 0.001
  	Should be an estimate for the energy gap [a.u.] (HOMO-LUMO) and is used in preconditioning, especially effective with the FULL_ALL preconditioner, in which case it should be an underestimate of the gap (0.001 doing normally fine). For the other preconditioners, making this value larger (0.2) will tame the preconditioner in case of poor initial guesses.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 2.00000000E-01

  EPS_IRAC
  	EPS_IRAC 1.0E-5
  	Targeted accuracy during the refinement iteration.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-10

  EPS_IRAC_FILTER_MATRIX
  	EPS_IRAC_FILTER_MATRIX 1.0E-5
  	Sets the threshold for filtering the matrices.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+00

  EPS_IRAC_QUICK_EXIT
  	EPS_IRAC_QUICK_EXIT 1.0E-2
  	Only one extra refinement iteration is done when the norm is below this value.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-05

  EPS_IRAC_SWITCH
  	EPS_IRAC_SWITCH 1.0E-3
  	The algorithm switches to the polynomial refinement when the norm is below this value.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-02

  EPS_TAYLOR
  	EPS_TAYLOR 1.0E-15
  	Target accuracy of the taylor expansion for the matrix functions, should normally be kept as is.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-16
  	Alias names for this keyword: EPSTAYLOR

  GOLD_TARGET
  	GOLD_TARGET 0.1
  	Target relative uncertainty in the location of the minimum for LINESEARCH GOLD
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-02

  IRAC_DEGREE
  	IRAC_DEGREE 4
  	The refinement polynomial degree (2, 3 or 4).
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 4

  LINESEARCH
  	LINESEARCH GOLD
  	1D line search algorithm to be used with the OT minimizer, in increasing order of robustness and cost. MINIMIZER CG combined with LINESEARCH GOLD should always find an electronic minimum. Whereas the 2PNT minimizer is almost always OK, 3PNT might be needed for systems in which successive OT CG steps do not decrease the total energy.
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: 2PNT
  	List of valid keywords: 2PNT extrapolate based on 2 points 3PNT ... or on 3 points GOLD perform 1D golden section search of the minimum (very expensive) NONE take fixed lenght steps
  	Alias names for this keyword: LINE_SEARCH

  MAX_IRAC
  	MAX_IRAC 5
  	Maximum allowed refinement iteration.
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 50

  MAX_TAYLOR
  	MAX_TAYLOR 5
  	Maximum order of the Taylor expansion before diagonalisation is prefered, for large parallel runs a slightly higher order could sometimes result in a small speedup.
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 4

  MINIMIZER
  	MINIMIZER DIIS
  	Minimizer to be used with the OT method
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: CG
  	List of valid keywords: BROYDEN Broyden mixing approximating the inverse Hessian CG Conjugate Gradients: most reliable, use for difficult systems. The total energy should decrease at every OT CG step if the line search is appropriate. DIIS Direct inversion in the iterative subspace: less reliable than CG, but sometimes about 50% faster SD Steepest descent: not recommended

  MIXED_PRECISION
  	MIXED_PRECISION T
  	Uses a mixed precision algorithm.With a well behaved basis set (i.e. condition number less than 1/eps_sp)it provides double precision accuracy results and up to a 2 fold speedup for building and applying the preconditioner.
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	Default value: .FALSE.

  NONDIAG_ENERGY
  	NONDIAG_ENERGY
  	Add a non-diagonal energy penalty (FD smearing)
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  NONDIAG_ENERGY_STRENGTH
  	NONDIAG_ENERGY_STRENGTH
  	The prefactor for the non-diagonal energy penalty (FD smearing)
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+00

  N_HISTORY_VEC
  	N_DIIS 4
  	Number of history vectors to be used with DIIS or BROYDEN
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 7
  	Alias names for this keyword: NDIIS, N_DIIS, N_BROYDEN

  OCCUPATION_PRECONDITIONER
  	OCCUPATION_PRECONDITIONER
  	Preconditioner with the occupation numbers (FD smearing)
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ON_THE_FLY_LOC
  	ON_THE_FLY_LOC T
  	On the fly localization of the molecular orbitals. Can only be used with OT/IRAC.
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	Default value: .FALSE.

  ORTHO_IRAC
  	ORTHO_IRAC POLY
  	The orthogonality method.
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: CHOL
  	List of valid keywords: CHOL Cholesky. LWDN Loewdin. POLY Polynomial.

  PRECONDITIONER
  	PRECONDITIONER FULL_ALL
  	Type of preconditioner to be used with all minimization schemes. They differ in effectiveness, cost of construction, cost of application. Properly preconditioned minimization can be orders of magnitude faster than doing nothing.
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: FULL_KINETIC
  	List of valid keywords: FULL_ALL Most effective state selective preconditioner based on diagonalization, requires the ENERGY_GAP parameter to be an underestimate of the HOMO-LUMO gap. This preconditioner is recommended for almost all systems, except very large systems where make_preconditioner would dominate the total computational cost. FULL_KINETIC Cholesky inversion of S and T, fast construction, robust, and relatively good, use for very large systems. FULL_SINGLE Based on H-eS diagonalisation, not as good as FULL_ALL, but somewhat cheaper to apply. FULL_SINGLE_INVERSE Based on H-eS cholesky inversion, similar to FULL_SINGLE in preconditioning efficiency but cheaper to construct, might be somewhat less robust. Recommended for large systems. FULL_S_INVERSE Cholesky inversion of S, not as good as FULL_KINETIC, yet equally expensive. NONE skip preconditioning SPARSE_DIAG Only based on atomic blocks, very cheap in construction but quite poor. SPARSE_KINETIC Toward -sparse- linear solver for T-eS. SPARSE_STABLE_APPROXIMATE_INVERSE Stabilized Approximate INVerse preconditioning using DBCSR sparse matrices (not working yet).
  	This keyword cites the following reference: [VandeVondele2003]

  PRECOND_SOLVER
  	PRECOND_SOLVER DIRECT
  	How the preconditioner is applied to the residual.
  	This optional keyword cannot be repeated and it expects precisely one keyword.
  	Default value: DEFAULT
  	List of valid keywords: DEFAULT the default DIRECT Cholesky decomposition followed by triangular solve (works for FULL_KINETIC/SINGLE_INVERSE/S_INVERSE) INVERSE_CHOLESKY Cholesky decomposition followed by explicit inversion (works for FULL_KINETIC/SINGLE_INVERSE/S_INVERSE) SAINV SAINV inversion (works for FULL_KINETIC/SINGLE_INVERSE/S_INVERSE)

  ROTATION
  	ROTATION
  	Introduce additional variables so that rotations of the occupied subspace are allowed as well, only needed for cases where the energy is not invariant under a rotation of the occupied subspace such as non-singlet restricted calculations or fractional occupations.
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  SAFE_DIIS
  	SAFE_DIIS ON
  	Reject DIIS steps if they point away from the minimum, do SD in that case.
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	Default value: .TRUE.
  	Alias names for this keyword: SAFER_DIIS

  SCP_DFT
  	SCP_DFT
  	Introduce additional self-consistent polarization through additional response basis functions (read in through AUX_BASIS.)
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  SCP_NDDO
  	SCP_NDDO
  	Introduce additional self-consistent polarization through response basis set = orbital basis set for NDDO.)
  	This optional keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  STEPSIZE
  	STEPSIZE 0.4
  	Initial stepsize used for the line search, sometimes this parameter can be reduced to stablize DIIS or to improve the CG behavior in the first few steps
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.50000000E-01