Section EWALD

• Ewald parameters controlling electrostatic only for CLASSICAL MM.

• Section path: CP2K_INPUT / FORCE_EVAL / MM / POISSON / EWALD

• This section cannot be repeated.

• This section cites the following references: [DARDEN1993] [ESSMANN1995] [Ewald1921] [Laino2008] [Toukmaji1996]

• Subsections

  • MULTIPOLES
  • PRINT
  • RS_GRID

• Keywords

  • ALPHA
  • EPSILON
  • EWALD_ACCURACY
  • EWALD_TYPE
  • GMAX
  • NS_MAX
  • O_SPLINE
  • RCUT

• Keyword descriptions

  ALPHA
  	ALPHA {Real}
  	alpha parameter associated with Ewald (EWALD|PME|SPME). Recommended for small systems is alpha = 3.5 / r_cut. For Tight-binding application a recommended value is alpha = 1.0. Tuning alpha, r_cut and gmax is needed to obtain O(N**1.5) scaling for ewald.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.50000000E-001
  	Default unit: [angstrom^-1]

  EPSILON
  	EPSILON {Real}
  	tolerance of gaussians for fft interpolation (PME only)
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-006

  EWALD_ACCURACY
  	EWALD_ACCURACY {Real}
  	Expected accuracy in the Ewald sum. This number affects only the calculation of the cutoff for the real-space term of the ewald summation (EWALD|PME|SPME) as well as the construction of the neighbor lists (if the cutoff for non-bonded terms is smaller than the value employed to compute the EWALD real-space term). This keyword has no effect on the reciprocal space term (which can be tuned independently).
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-006
  	Default unit: [hartree]

  EWALD_TYPE
  	EWALD_TYPE {Keyword}
  	The type of ewald you want to perform.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: EWALD
  	List of valid keywords: EWALD EWALD is the standard non-fft based ewald NONE NONE standard real-space coulomb potential is computed together with the non-bonded contributions PME PME is the particle mesh using fft interpolation SPME SPME is the smooth particle mesh using beta-Euler splines (recommended)
  	This keyword cites the following references: [DARDEN1993] [ESSMANN1995] [Ewald1921]

  GMAX
  	GMAX {Integer} ...
  	number of grid points (SPME and EWALD). If a single number is specified,the same number of points is used for all three directions on the grid.If three numbers are given, each direction can have a different number of points.The number of points needs to be FFTable (which depends on the library used) and odd for EWALD.The optimal number depends e.g. on alpha and the size of the cell. 1 point per Angstrom is common.
  	This keyword cannot be repeated and it expects a list of integers.

  NS_MAX
  	NS_MAX {Integer}
  	number of grid points on small mesh (PME only), should be odd.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 11

  O_SPLINE
  	O_SPLINE {Integer}
  	order of the beta-Euler spline (SPME only)
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 6

  RCUT
  	RCUT {Real}
  	Explicitly provide the real-space cutoff of the ewald summation (EWALD|PME|SPME). This value is ignored in Tight-binding applications (rcut from basis overlap is used). If present, overwrites the estimate of EWALD_ACCURACY and may affect the construction of the neighbor lists for non-bonded terms (in FIST), if the value specified is larger than the cutoff for non-bonded interactions.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default unit: [angstrom]