git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@7860 f3b2605a-c512-4ea7-a41b-209d697bcdaa
This commit is contained in:
sjplimp
@ -23,8 +23,9 @@
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x,y,z = PPPM FFT grid size in each dimension
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<I>order</I> value = N
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N = grid extent of Gaussian for PPPM mapping of each charge
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<I>gewald</I> value = r
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r = PPPM G-ewald parameter
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<I>force</I> value = accuracy (force units)
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<I>gewald</I> value = rinv (1/distance units)
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rinv = PPPM G-ewald parameter
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<I>slab</I> value = volfactor
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volfactor = ratio of the total extended volume used in the
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2d approximation compared with the volume of the simulation domain
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@ -66,15 +67,25 @@ small problems are run on large numbers of processors. A warning will
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be generated indicating the order parameter is being reduced to allow
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LAMMPS to run the problem.
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</P>
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<P>The <I>force</I> keyword overrides the relative accuracy parameter set by
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the <A HREF = "kspace_style.html">kspace_style</A> command with an absolute
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accuracy. The accuracy determines the RMS error in per-atom forces
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calculated by the long-range solver and is thus specified in force
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units. A negative value for the accuracy setting means to use the
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relative accuracy parameter. The accuracy setting is used in
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conjunction with the pairwise cutoff to determine the number of
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K-space vectors for style <I>ewald</I> or the FFT grid size for style
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<I>pppm</I>.
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</P>
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<P>The <I>gewald</I> keyword sets the value of the Ewald or PPPM G-ewald
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parameter. Without this setting, LAMMPS chooses the parameter
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automatically as a function of cutoff, precision, grid spacing, etc.
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This means it can vary from one simulation to the next which may not
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be desirable for matching a KSpace solver to a pre-tabulated pairwise
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potential. This setting can also be useful if Ewald or PPPM fails to
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choose a good grid spacing and G-ewald parameter automatically. If
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the value is set to 0.0, LAMMPS will choose the G-ewald parameter
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automatically.
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parameter as <I>rinv</I> in reciprocal distance units. Without this
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setting, LAMMPS chooses the parameter automatically as a function of
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cutoff, precision, grid spacing, etc. This means it can vary from one
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simulation to the next which may not be desirable for matching a
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KSpace solver to a pre-tabulated pairwise potential. This setting can
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also be useful if Ewald or PPPM fails to choose a good grid spacing
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and G-ewald parameter automatically. If the value is set to 0.0,
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LAMMPS will choose the G-ewald parameter automatically.
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</P>
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<P>The <I>slab</I> keyword allows an Ewald or PPPM solver to be used for a
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systems that are periodic in x,y but non-periodic in z - a
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@ -98,8 +109,8 @@ option is explained in the paper by <A HREF = "#Yeh">(Yeh)</A>.
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</P>
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<P><B>Default:</B>
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</P>
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<P>The option defaults are mesh = 0 0 0, order = 5, gewald = 0.0, and
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slab = 1.0.
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<P>The option defaults are mesh = 0 0 0, order = 5, force = -1.0, gewald
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= 0.0, and slab = 1.0.
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</P>
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<HR>
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@ -18,8 +18,9 @@ keyword = {mesh} or {order} or {gewald} or {slab} :l
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x,y,z = PPPM FFT grid size in each dimension
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{order} value = N
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N = grid extent of Gaussian for PPPM mapping of each charge
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{gewald} value = r
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r = PPPM G-ewald parameter
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{force} value = accuracy (force units)
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{gewald} value = rinv (1/distance units)
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rinv = PPPM G-ewald parameter
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{slab} value = volfactor
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volfactor = ratio of the total extended volume used in the
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2d approximation compared with the volume of the simulation domain :pre
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@ -60,15 +61,25 @@ small problems are run on large numbers of processors. A warning will
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be generated indicating the order parameter is being reduced to allow
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LAMMPS to run the problem.
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The {force} keyword overrides the relative accuracy parameter set by
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the "kspace_style"_kspace_style.html command with an absolute
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accuracy. The accuracy determines the RMS error in per-atom forces
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calculated by the long-range solver and is thus specified in force
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units. A negative value for the accuracy setting means to use the
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relative accuracy parameter. The accuracy setting is used in
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conjunction with the pairwise cutoff to determine the number of
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K-space vectors for style {ewald} or the FFT grid size for style
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{pppm}.
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The {gewald} keyword sets the value of the Ewald or PPPM G-ewald
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parameter. Without this setting, LAMMPS chooses the parameter
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automatically as a function of cutoff, precision, grid spacing, etc.
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This means it can vary from one simulation to the next which may not
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be desirable for matching a KSpace solver to a pre-tabulated pairwise
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potential. This setting can also be useful if Ewald or PPPM fails to
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choose a good grid spacing and G-ewald parameter automatically. If
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the value is set to 0.0, LAMMPS will choose the G-ewald parameter
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automatically.
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parameter as {rinv} in reciprocal distance units. Without this
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setting, LAMMPS chooses the parameter automatically as a function of
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cutoff, precision, grid spacing, etc. This means it can vary from one
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simulation to the next which may not be desirable for matching a
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KSpace solver to a pre-tabulated pairwise potential. This setting can
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also be useful if Ewald or PPPM fails to choose a good grid spacing
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and G-ewald parameter automatically. If the value is set to 0.0,
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LAMMPS will choose the G-ewald parameter automatically.
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The {slab} keyword allows an Ewald or PPPM solver to be used for a
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systems that are periodic in x,y but non-periodic in z - a
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@ -92,8 +103,8 @@ option is explained in the paper by "(Yeh)"_#Yeh.
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[Default:]
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The option defaults are mesh = 0 0 0, order = 5, gewald = 0.0, and
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slab = 1.0.
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The option defaults are mesh = 0 0 0, order = 5, force = -1.0, gewald
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= 0.0, and slab = 1.0.
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:line
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@ -18,25 +18,25 @@
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<UL><LI>style = <I>none</I> or <I>ewald</I> or <I>pppm</I> or <I>pppm/cg</I> or <I>pppm/tip4p</I> or <I>ewald/n</I> or <I>pppm/gpu</I> or <I>ewald/omp</I> or <I>pppm/omp</I> or <I>pppm/proxy</I>
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<PRE> <I>none</I> value = none
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<I>ewald</I> value = precision
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precision = desired accuracy
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<I>pppm</I> value = precision
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precision = desired accuracy
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<I>pppm/cg</I> value = precision (smallq)
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precision = desired accuracy
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<I>ewald</I> value = accuracy
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accuracy = desired relative error in forces
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<I>pppm</I> value = accuracy
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accuracy = desired relative error in forces
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<I>pppm/cg</I> value = accuracy (smallq)
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accuracy = desired relative error in forces
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smallq = cutoff for charges to be considered (optional) (charge units)
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<I>pppm/tip4p</I> value = precision
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precision = desired accuracy
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<I>ewald/n</I> value = precision
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precision = desired accuracy
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<I>pppm/gpu</I> value = precision
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precision = desired accuracy
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<I>ewald/omp</I> value = precision
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precision = desired accuracy
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<I>pppm/omp</I> value = precision
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precision = desired accuracy
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<I>pppm/proxy</I> value = precision
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precision = desired accuracy
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<I>pppm/tip4p</I> value = accuracy
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accuracy = desired relative error in forces
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<I>ewald/n</I> value = accuracy
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accuracy = desired relative error in forces
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<I>pppm/gpu</I> value = accuracy
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accuracy = desired relative error in forces
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<I>ewald/omp</I> value = accuracy
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accuracy = desired relative error in forces
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<I>pppm/omp</I> value = accuracy
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accuracy = desired relative error in forces
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<I>pppm/proxy</I> value = accuracy
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accuracy = desired relative error in forces
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</PRE>
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</UL>
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@ -119,13 +119,23 @@ dispersion forces in a Lennard-Jones or Buckingham potential, see the
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<A HREF = "pair_lj_coul.html">pair_style lj/coul</A> or <A HREF = "pair_buck_coul.html">pair_style
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buck/coul</A> commands.
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</P>
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<P>A precision value of 1.0e-4 means one part in 10000. This setting is
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used in conjunction with the pairwise cutoff to determine the number
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of K-space vectors for style <I>ewald</I> or the FFT grid size for style
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<I>pppm</I>.
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<P>The specified <I>accuracy</I> determines the relative RMS error in per-atom
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forces calculated by the long-range solver. It is set as a
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dimensionless number, relative to the force that two unit point
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charges (e.g. 2 monovalent ions) exert on each other at a distance of
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1 Angstrom. This reference value was chosen as representative of the
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magnitude of electrostatic forces in atomic systems. Thus an accuracy
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value of 1.0e-4 means that the RMS error will be a factor of 10000
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smaller than the reference force.
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</P>
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<P>The accuracy setting is used in conjunction with the pairwise cutoff
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to determine the number of K-space vectors for style <I>ewald</I> or the
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FFT grid size for style <I>pppm</I>.
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</P>
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<P>See the <A HREF = "kspace_modify.html">kspace_modify</A> command for additional
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options of the K-space solvers that can be set.
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options of the K-space solvers that can be set, including a <I>force</I>
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option for setting an absoulte RMS error in forces, as opposed to a
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relative RMS error.
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</P>
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<HR>
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@ -14,25 +14,25 @@ kspace_style style value :pre
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style = {none} or {ewald} or {pppm} or {pppm/cg} or {pppm/tip4p} or {ewald/n} or {pppm/gpu} or {ewald/omp} or {pppm/omp} or {pppm/proxy} :ulb,l
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{none} value = none
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{ewald} value = precision
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precision = desired accuracy
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{pppm} value = precision
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precision = desired accuracy
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{pppm/cg} value = precision (smallq)
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precision = desired accuracy
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{ewald} value = accuracy
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accuracy = desired relative error in forces
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{pppm} value = accuracy
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accuracy = desired relative error in forces
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{pppm/cg} value = accuracy (smallq)
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accuracy = desired relative error in forces
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smallq = cutoff for charges to be considered (optional) (charge units)
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{pppm/tip4p} value = precision
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precision = desired accuracy
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{ewald/n} value = precision
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precision = desired accuracy
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{pppm/gpu} value = precision
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precision = desired accuracy
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{ewald/omp} value = precision
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precision = desired accuracy
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{pppm/omp} value = precision
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precision = desired accuracy
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{pppm/proxy} value = precision
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precision = desired accuracy :pre
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{pppm/tip4p} value = accuracy
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accuracy = desired relative error in forces
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{ewald/n} value = accuracy
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accuracy = desired relative error in forces
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{pppm/gpu} value = accuracy
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accuracy = desired relative error in forces
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{ewald/omp} value = accuracy
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accuracy = desired relative error in forces
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{pppm/omp} value = accuracy
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accuracy = desired relative error in forces
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{pppm/proxy} value = accuracy
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accuracy = desired relative error in forces :pre
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:ule
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[Examples:]
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@ -114,13 +114,23 @@ dispersion forces in a Lennard-Jones or Buckingham potential, see the
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"pair_style lj/coul"_pair_lj_coul.html or "pair_style
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buck/coul"_pair_buck_coul.html commands.
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A precision value of 1.0e-4 means one part in 10000. This setting is
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used in conjunction with the pairwise cutoff to determine the number
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of K-space vectors for style {ewald} or the FFT grid size for style
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{pppm}.
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The specified {accuracy} determines the relative RMS error in per-atom
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forces calculated by the long-range solver. It is set as a
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dimensionless number, relative to the force that two unit point
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charges (e.g. 2 monovalent ions) exert on each other at a distance of
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1 Angstrom. This reference value was chosen as representative of the
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magnitude of electrostatic forces in atomic systems. Thus an accuracy
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value of 1.0e-4 means that the RMS error will be a factor of 10000
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smaller than the reference force.
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The accuracy setting is used in conjunction with the pairwise cutoff
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to determine the number of K-space vectors for style {ewald} or the
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FFT grid size for style {pppm}.
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See the "kspace_modify"_kspace_modify.html command for additional
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options of the K-space solvers that can be set.
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options of the K-space solvers that can be set, including a {force}
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option for setting an absoulte RMS error in forces, as opposed to a
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relative RMS error.
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:line
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