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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@8932 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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pscrozi
2012-10-10 00:35:57 +00:00
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doc/kspace_modify.txt
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@ -19,11 +19,9 @@ keyword = {mesh} or {order} or {gewald} or {slab} or (nozforce} or {compute} or
{mesh/disp} value = x y z
x,y,z = grid size in each dimension for 1/r^6 dispersion
{order} value = N
N = gridextent of Gaussian for PPPM or MSM mapping of charge to grid
N = extent of Gaussian for PPPM or MSM mapping of charge to grid
{order/disp} value = N
N = extent of Gaussian for PPPM mapping of dispersion term to grid
{order/split} value = N
N = order of Taylor series used to split the potential between different MSM levels
{force} value = accuracy (force units)
{gewald} value = rinv (1/distance units)
rinv = G-ewald parameter for Coulombics
@ -39,7 +37,7 @@ keyword = {mesh} or {order} or {gewald} or {slab} or (nozforce} or {compute} or
[Examples:]
kspace_modify mesh 24 24 30 order 6 order/split 3
kspace_modify mesh 24 24 30 order 6
kspace_modify slab 3.0 :pre
[Description:]
@ -60,7 +58,7 @@ user-specified accuracy and pairwise cutoff. Values for x,y,z of
The {mesh/disp} keyword sets the grid size for kspace style
{pppm/disp}. This is the FFT mesh for long-range dispersion and ach
dimension must be factorizable into powers of 2, 3, and 5. When this
option is not set, the PPPM solver chooses its own grid size,
option is not set, the PPPM solver chooses its own grid size,
consistent with the user-specified accuracy and pairwise cutoff.
Values for x,y,z of 0,0,0 unset the option.
@ -82,14 +80,6 @@ dispersion term extends when it is mapped to the grid in kspace style
{pppm/disp}. It has the same meaning as the {order} setting for
Coulombics.
The {order/split} keyword determines the order of the Taylor series
used to split the potential between different MSM grid levels, and can
range from 2 and 6. "(Hardy)"_#Hardy recommends that the {order/split}
be roughly half of the order parameter. For example, the default MSM
order is 4 and the default split order is 2. For higher accuracy in
MSM, one can use order 10 and {order/split} 5 or 6, though this will
increase the interpolation cost as described above.
The PPPM order parameter may be reset by LAMMPS when it sets up the
FFT grid if the implied grid stencil extends beyond the grid cells
owned by neighboring processors. Typically this will only occur when
@ -173,16 +163,10 @@ option. Support for those {pppm} variants will be added later.
[Default:]
The option defaults are mesh = mesh/disp = 0 0 0, order = order/disp =
5 (PPPM), order = 4 (MSM), order/split = 2 (MSM), force = -1.0, gewald
= gewald/disp = 0.0, slab = 1.0, compute = yes, and diff = ik (PPPM),
diff = ad (MSM).
5 (PPPM), order = 4 (MSM), force = -1.0, gewald = gewald/disp = 0.0,
slab = 1.0, compute = yes, and diff = ik (PPPM), diff = ad (MSM).
:line
:link(Yeh)
[(Yeh)] Yeh and Berkowitz, J Chem Phys, 111, 3155 (1999).
:link(Hardy)
[(Hardy)] David, Multilevel Summation for the Fast Evaluation of
Forces for the Simulation of Biomolecules, University of Illinois
at Urbana-Champaign, (2006).