Section PEXSI

• Specifies the parameters of the PEXSI library. The density matrix is calculated with PEXSI if PURIFICATION_METHOD (in LS_SCF section) is set to PEXSI. The computational cost of PEXSI is at most quadratically scaling w.r.t. the system size and PEXSI is applicable to insulating and metallic systems. The value of EPS_PGF_ORB (in QS input section) defines the sparsity of the matrices sent to PEXSI and EPS_FILTER is overwritten with 0.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / LS_SCF / PEXSI

• This section cannot be repeated.

• This section cites the following references: [Lin2009] [Lin2013]

• Subsections

  • none

• Keywords

  • CSR_SCREENING
  • GAP
  • IS_INERTIA_COUNT
  • MAX_PEXSI_ITER
  • MIN_RANKS_PER_POLE
  • MU_INERTIA_EXPANSION
  • MU_INERTIA_TOLERANCE
  • MU_MAX_0
  • MU_MIN_0
  • MU_PEXSI_SAFE_GUARD
  • NP_SYMB_FACT
  • NUM_ELECTRON_INITIAL_TOLERANCE
  • NUM_ELECTRON_PEXSI_TOLERANCE
  • NUM_POLE
  • ORDERING
  • TEMPERATURE
  • VERBOSITY

• Keyword descriptions

  CSR_SCREENING
  	CSR_SCREENING {Logical}
  	Whether distance screening should be applied to improve sparsity of CSR matrices.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .TRUE.

  GAP
  	GAP {Real}
  	Spectral gap. Note: This can be set to be 0 in most cases.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000
  	Default unit: [hartree]

  IS_INERTIA_COUNT
  	IS_INERTIA_COUNT {Logical}
  	Whether inertia counting is used each time the DFT driver of PEXSI is invoked. If FALSE, inertia counting is still used in the first SCF iteration.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  MAX_PEXSI_ITER
  	MAX_PEXSI_ITER {Integer}
  	Maximum number of PEXSI iterations after each inertia counting procedure.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 5

  MIN_RANKS_PER_POLE
  	MIN_RANKS_PER_POLE {Integer}
  	The minimum number of processors used for each pole. The real number of processors per pole is the smallest number greater or equal to MIN_RANKS_PER_POLE that divides MPI size without remainder. For efficiency, MIN_RANKS_PER_POLE should be a small numbers (limited by the available memory).
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 64

  MU_INERTIA_EXPANSION
  	MU_INERTIA_EXPANSION {Real}
  	If the chemical potential is not in the initial interval, the interval is expanded by MU_INERTIA_EXPANSION.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.50000000E-001
  	Default unit: [hartree]

  MU_INERTIA_TOLERANCE
  	MU_INERTIA_TOLERANCE {Real}
  	Stopping criterion in terms of the chemical potential for the inertia counting procedure.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-002
  	Default unit: [hartree]

  MU_MAX_0
  	MU_MAX_0 {Real}
  	Initial guess of upper bound for mu.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E+000
  	Default unit: [hartree]

  MU_MIN_0
  	MU_MIN_0 {Real}
  	Initial guess of lower bound for mu.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: -5.00000000E+000
  	Default unit: [hartree]

  MU_PEXSI_SAFE_GUARD
  	MU_PEXSI_SAFE_GUARD {Real}
  	Safe guard criterion in terms of the chemical potential to reinvoke the inertia counting procedure.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-002
  	Default unit: [hartree]

  NP_SYMB_FACT
  	NP_SYMB_FACT {Integer}
  	Number of processors for PARMETIS/PT-SCOTCH. Only used if the ordering == 0. If 0, the number of processors for PARMETIS/PT-SCOTCH will be set equal to the number of MPI ranks per pole. Note: if more than one processor is used, a segmentation fault may occur in the symbolic factorization phase.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 1

  NUM_ELECTRON_INITIAL_TOLERANCE
  	NUM_ELECTRON_INITIAL_TOLERANCE {Real}
  	The same as NUM_ELECTRON_PEXSI_TOLERANCE but applied in the first SCF steps. If set to a value smaller than NUM_ELECTRON_PEXSI_TOLERANCE, it is overwritten with NUM_ELECTRON_PEXSI_TOLERANCE (default). If set to a value larger than NUM_ELECTRON_PEXSI_TOLERANCE, the PEXSI tolerance in number of electrons is set adaptively according to the SCF convergence error of the previous SCF step. This reduces the number of PEXSI iterations in the first SCF steps but leads to at least one more SCF step.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000

  NUM_ELECTRON_PEXSI_TOLERANCE
  	NUM_ELECTRON_PEXSI_TOLERANCE {Real}
  	Stopping criterion of the PEXSI iteration in terms of The number of electrons compared to the exact number of electrons. This threshold is the target tolerance applied at convergence of SCF.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-001

  NUM_POLE
  	NUM_POLE {Integer}
  	Number of terms in the pole expansion (should be even).
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 64

  ORDERING
  	ORDERING {Keyword}
  	Ordering strategy for factorization and selected inversion.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: PARALLEL
  	List of valid keywords: MULTIPLE_MINIMUM_DEGREE Multiple minimum degree ordering (MMD_AT_PLUS_A option in SuperLU_DIST) PARALLEL Parallel ordering using ParMETIS/PT-SCOTCH (PARMETIS option in SuperLU_DIST) SEQUENTIAL Sequential ordering using METIS (METIS_AT_PLUS_A option in SuperLU_DIST)

  TEMPERATURE
  	TEMPERATURE {Real}
  	Electronic temperature
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E+002
  	Default unit: [K]

  VERBOSITY
  	VERBOSITY {Keyword}
  	The level of output information.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: BASIC
  	List of valid keywords: BASIC Without description, yet. DETAILED Without description, yet. SILENT Without description, yet.