Section EWALD

• Ewald parameters controlling electrostatic only for CLASSICAL MM.

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

• This section cannot be repeated and can be optional.

• 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 .30
  	alpha parameter associated with Ewald (EWALD|PME|SPME). Recommended for small systems is is alpha = 3.5 / r_cut. Tuning alpha, r_cut and gmax is needed to obtain O(N**1.5) scaling for ewald.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.50000000E-01
  	Default unit: [angstrom^-1]

  EPSILON
  	EPSILON 1E-6
  	tolerance of gaussians for fft interpolation (PME only)
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-06

  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 optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-06
  	Default unit: [hartree]

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

  GMAX
  	GMAX 25 25 25
  	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 optional keyword cannot be repeated and it expects a list of integers.

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

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

  RCUT
  	RCUT 5.0
  	Explicitly provide the real-space cutoff of the ewald summation (EWALD|PME|SPME). 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 optional keyword cannot be repeated and it expects precisely one real.
  	Default unit: [angstrom]