Section LOW_SCALING

• Cubic scaling RI-RPA, GW and Laplace-SOS-MP2 method using the imaginary time formalism. EPS_GRID in WFC_GPW section controls accuracy / req. memory for 3-center integrals. SORT_BASIS EXP should be specified in DFT section.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / XC / WF_CORRELATION / LOW_SCALING

• This section cannot be repeated.

• Subsections

  • none

• Keywords

  • SECTION_PARAMETERS
  • CUTOFF_W
  • DO_KPOINTS
  • EPS_FILTER
  • EPS_FILTER_FACTOR
  • EPS_STORAGE_SCALING
  • EXP_KPOINTS
  • KPOINTS
  • MEMORY_CUT
  • MEMORY_INFO
  • MIN_BLOCK_SIZE
  • MIN_BLOCK_SIZE_MO

• Keyword descriptions

  SECTION_PARAMETERS
  	&LOW_SCALING {Logical}
  	Activates cubic-scaling RPA, GW and Laplace-SOS-MP2 calculations.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  CUTOFF_W
  	CUTOFF_W {Real}
  	Cutoff for screened Coulomb interaction for GW kpoints.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-001

  DO_KPOINTS
  	DO_KPOINTS {Logical}
  	Besides in DFT, this keyword has to be switched on if one wants to do kpoints in. cubic RPA.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  EPS_FILTER
  	EPS_FILTER {Real}
  	Determines a threshold for the DBCSR based multiply.Normally, this EPS_FILTER determines accuracy and timing of low-scaling RPA and GW calculations.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-009

  EPS_FILTER_FACTOR
  	EPS_FILTER_FACTOR {Real}
  	Multiply EPS_FILTER with this factor to determine filter epsilon for DBCSR based multiply P(it)=(Mocc(it))^T*Mvirt(it) Default should be kept.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+001

  EPS_STORAGE_SCALING
  	EPS_STORAGE_SCALING {Real}
  	Scaling factor to scale EPS_FILTER. Storage threshold for compression will be EPS_FILTER*EPS_STORAGE_SCALING.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-003
  	Alias names for this keyword: EPS_STORAGE

  EXP_KPOINTS
  	EXP_KPOINTS {Real}
  	For kpoints in low-scaling GW, a Monkhorst-Pack mesh is used. Because the screened Coulomb interaction W(k) diverges at the Gamma point with W(k) ~ k^alpha, we adapt the weights of the Monkhorst-Pack mesh to compute int_BZ k^alpha dk (BZ=Brllouin zone) correctly with the Monkhorst-Pack mesh. You can enter here the exponent alpha. For solids, the exponent is -2 (known from plane waves), for 2d periodic systems -1 and for 1d systems W(k) ~ log(1-cos(a*k)) where a is the length of the unit cell in periodic direction. If you enter 1.0, one of these three functions are picked according to the periodicity. If you enter a value bigger than 2.0, the ordinary Monkhorst-Pack mesh with identical weights is chosen.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+000

  KPOINTS
  	KPOINTS {Integer} {Integer} {Integer}
  	For periodic calculations, using kpoints for the density response and the Coulomb operator are strongly recommended. For 2d periodic systems (e.g. xy periodicity, please specify KPOINTS N_x 0 N_z.
  	This keyword cannot be repeated and it expects precisely 3 integers.
  	Default values: 0 0 0

  MEMORY_CUT
  	MEMORY_CUT {Integer}
  	Reduces memory for sparse tensor contractions by this factor. A high value leads to some loss of performance. This memory reduction factor applies to storage of the tensors 'M occ' / 'M virt' but does not reduce storage of '3c ints'.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 5

  MEMORY_INFO
  	MEMORY_INFO {Logical}
  	Decide whether to print memory info on the sparse matrices.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  MIN_BLOCK_SIZE
  	MIN_BLOCK_SIZE {Integer}
  	Minimum tensor block size. Adjusting this value may have minor effect on performance but default should be good enough.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 5

  MIN_BLOCK_SIZE_MO
  	MIN_BLOCK_SIZE_MO {Integer}
  	Tensor block size for MOs. Only relevant for GW calculations. The memory consumption of GW scales as O(MIN_BLOCK_SIZE_MO). It is recommended to set this parameter to a smaller number if GW runs out of memory. Otherwise the default should not be changed.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 64