enable pppm/tip4p to work with triclinic

doc/src/Section_commands.txt

@@ -581,7 +581,7 @@ USER-INTEL, k = KOKKOS, o = USER-OMP, t = OPT.
 "indent"_fix_indent.html,
 "langevin (k)"_fix_langevin.html,
 "lineforce"_fix_lineforce.html,
-"momentum"_fix_momentum.html,
+"momentum (k)"_fix_momentum.html,
 "move"_fix_move.html,
 "msst"_fix_msst.html,
 "neb"_fix_neb.html,

doc/src/fix_momentum.txt

@@ -7,6 +7,7 @@
 :line
 
 fix momentum command :h3
+fix momentum/kk command :h3
 
 [Syntax:]
 
@@ -55,6 +56,29 @@ of atoms by rescaling the velocities after the momentum was removed.
 Note that the "velocity"_velocity.html command can be used to create
 initial velocities with zero aggregate linear and/or angular momentum.
 
+:line
+
+Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
+functionally the same as the corresponding style without the suffix.
+They have been optimized to run faster, depending on your available
+hardware, as discussed in "Section 5"_Section_accelerate.html
+of the manual.  The accelerated styles take the same arguments and
+should produce the same results, except for round-off and precision
+issues.
+
+These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
+USER-OMP and OPT packages, respectively.  They are only enabled if
+LAMMPS was built with those packages.  See the "Making
+LAMMPS"_Section_start.html#start_3 section for more info.
+
+You can specify the accelerated styles explicitly in your input script
+by including their suffix, or you can use the "-suffix command-line
+switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
+use the "suffix"_suffix.html command in your input script.
+
+See "Section 5"_Section_accelerate.html of the manual for
+more instructions on how to use the accelerated styles effectively.
+
 [Restart, fix_modify, output, run start/stop, minimize info:]
 
 No information about this fix is written to "binary restart

doc/src/lammps.book

@@ -214,6 +214,7 @@ fix_nve_manifold_rattle.html
 fix_nve_noforce.html
 fix_nve_sphere.html
 fix_nve_tri.html
+fix_nvk.html
 fix_nvt_asphere.html
 fix_nvt_body.html
 fix_nvt_manifold_rattle.html