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3.12. Kspace styles

Classes that compute long-range Coulombic interactions via K-space representations (Ewald, PPPM) are derived from the KSpace class. New styles can be created to add new K-space options to LAMMPS.

src/ewald.cpp is an example of computing K-space interactions.

Here is a brief description of methods you define in your new derived class. See src/kspace.h for details.

Required	“pure” methods that must be overridden in a derived class
init	initialize the calculation before a run
setup	computation before the first timestep of a run
compute	every-timestep computation

Optional	methods that have a default or empty implementation
settings	process the arguments to the kspace_style command
compute_group_group	compute energy/force between two groups of atoms
qsum_qsq	compute total charge and charge-squared sum
reset_grid	called when the FFT grid size changes
pack_forward_grid	pack FFT grid data into a buffer for forward communication
unpack_forward_grid	unpack FFT grid data from a forward communication buffer
pack_reverse_grid	pack FFT grid data into a buffer for reverse communication
unpack_reverse_grid	unpack FFT grid data from a reverse communication buffer
timing	report timing information (used by kspace_modify)
timing_1d	report 1d FFT timing
timing_3d	report 3d FFT timing
modify_param	handle arguments from the kspace_modify command
memory_usage	tally of memory usage

Here is a list of flags or settings that should be set in the constructor of the derived class when they differ from the default setting.

Name of flag	Description	default
ewaldflag	1 if this is an Ewald solver	0
pppmflag	1 if this is a PPPM solver	0
msmflag	1 if this is an MSM solver	0
dispersionflag	1 if this is a LJ/dispersion solver	0
tip4pflag	1 if this is a TIP4P solver	0
dipoleflag	1 if this is a dipole solver	0
spinflag	1 if this is a spin solver	0
triclinic_support	1 if the style supports triclinic boxes	1
group_group_enable	1 if compute_group_group() is implemented	0
centroidstressflag	CENTROID_SAME/CENTROID_AVAIL/CENTROID_NOTAVAIL	NOTAV.

The pair-style flags ewaldflag, pppmflag, msmflag, dispersionflag, tip4pflag, dipoleflag, and spinflag must match the corresponding flags set in the pair style that is used together with the kspace style. The default value of centroidstressflag is CENTROID_NOTAVAIL for kspace styles, as the centroid stress for long-range interactions is generally not equal to the two-body virial.