Back to the main page of this manual  Input reference of CP2K version 2023.1 (Development Version) 
CP2K_INPUT /
FORCE_EVAL /
QMMM /
PERIODIC /
POISSON /
EWALD
ALPHA {Real} 

alpha parameter associated with Ewald (EWALDPMESPME). Recommended for small systems is alpha = 3.5 / r_cut. For Tightbinding 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. [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one real.  
Default value:
3.50000000E001 

Default unit:
[angstrom^1]

EPSILON {Real} 

tolerance of gaussians for fft interpolation (PME only) [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one real.  
Default value:
1.00000000E006 
EWALD_ACCURACY {Real} 

Expected accuracy in the Ewald sum. This number affects only the calculation of the cutoff for the realspace term of the ewald summation (EWALDPMESPME) as well as the construction of the neighbor lists (if the cutoff for nonbonded terms is smaller than the value employed to compute the EWALD realspace term). This keyword has no effect on the reciprocal space term (which can be tuned independently). [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one real.  
Default value:
1.00000000E006 

Default unit:
[hartree]

EWALD_TYPE {Keyword} 

The type of ewald you want to perform. [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one keyword.  
Default value:
EWALD 

List of valid keywords:


This keyword cites the following references: [DARDEN1993] [ESSMANN1995] [Ewald1921] 
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. [Edit on GitHub]  
This keyword cannot be repeated and it expects a list of integers. 
NS_MAX {Integer} 

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

order of the betaEuler spline (SPME only) [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one integer.  
Default value:
6 
RCUT {Real} 

Explicitly provide the realspace cutoff of the ewald summation (EWALDPMESPME). This value is ignored in Tightbinding 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 nonbonded terms (in FIST), if the value specified is larger than the cutoff for nonbonded interactions. [Edit on GitHub]  
This keyword cannot be repeated and it expects precisely one real.  
Default unit:
[angstrom]

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