use more obvious pair style dpd thermostat examples

doc/src/pair_dpd.rst

@@ -26,8 +26,8 @@ Syntax
    pair_style dpd T cutoff seed
    pair_style dpd/tstat Tstart Tstop cutoff seed
 
-* T = temperature (temperature units)
+* T = temperature (temperature units) (dpd only)
-* Tstart,Tstop = desired temperature at start/end of run (temperature units)
+* Tstart,Tstop = desired temperature at start/end of run (temperature units) (dpd/tstat only)
 * cutoff = global cutoff for DPD interactions (distance units)
 * seed = random # seed (positive integer)
 
@@ -40,9 +40,9 @@ Examples
    pair_coeff * * 3.0 1.0
    pair_coeff 1 1 3.0 1.0 1.0
 
-   pair_style dpd/tstat 1.0 1.0 2.5 34387
+   pair_style hybrid/overlay lj/cut 2.5 dpd/tstat 1.0 1.0 2.5 34387
-   pair_coeff * * 1.0
+   pair_coeff * * lj/cut 1.0 1.0
-   pair_coeff 1 1 1.0 1.0
+   pair_coeff * * dpd/tstat 1.0
 
 Description
 """""""""""
@@ -53,7 +53,7 @@ Style *dpd* computes a force field for dissipative particle dynamics
 Style *dpd/tstat* invokes a DPD thermostat on pairwise interactions,
 which is equivalent to the non-conservative portion of the DPD force
 field.  This pairwise thermostat can be used in conjunction with any
-:doc:`pair style <pair_style>`, and in leiu of per-particle thermostats
+:doc:`pair style <pair_style>`, and instead of per-particle thermostats
 like :doc:`fix langevin <fix_langevin>` or ensemble thermostats like
 Nose Hoover as implemented by :doc:`fix nvt <fix_nh>`.  To use
 *dpd/tstat* as a thermostat for another pair style, use the
@@ -105,14 +105,18 @@ commands:
 * :math:`\gamma` (force/velocity units)
 * cutoff (distance units)
 
-The last coefficient is optional.  If not specified, the global DPD
+The cutoff coefficient is optional.  If not specified, the global DPD
 cutoff is used.  Note that sigma is set equal to sqrt(2 T gamma),
 where T is the temperature set by the :doc:`pair_style <pair_style>`
 command so it does not need to be specified.
 
 For style *dpd/tstat*, the coefficients defined for each pair of
-atoms types via the :doc:`pair_coeff <pair_coeff>` command is the same,
+atoms types via the :doc:`pair_coeff <pair_coeff>` command are:
-except that A is not included.
+
+* :math:`\gamma` (force/velocity units)
+* cutoff (distance units)
+
+The cutoff coefficient is optional.
 
 The GPU-accelerated versions of these styles are implemented based on
 the work of :ref:`(Afshar) <Afshar>` and :ref:`(Phillips) <Phillips>`.
@@ -135,6 +139,12 @@ the work of :ref:`(Afshar) <Afshar>` and :ref:`(Phillips) <Phillips>`.
    numbers are applied and thus the individual forces and therefore
    also the virial/pressure.
 
+.. note::
+
+   For more consistent time integration and force computation you may
+   consider using :doc:`fix mvv/dpd <fix_mvv_dpd>` instead of :doc:`fix
+   nve <fix_nve>`.
+
 ----------
 
 .. include:: accel_styles.rst
@@ -206,7 +216,9 @@ command for more details.
 Related commands
 """"""""""""""""
 
-:doc:`pair_coeff <pair_coeff>`, :doc:`fix nvt <fix_nh>`, :doc:`fix langevin <fix_langevin>`, :doc:`pair_style srp <pair_srp>`
+:doc:`pair_style dpd/ext <pair_dpd_ext>`, :doc:`pair_coeff <pair_coeff>`,
+:doc:`fix nvt <fix_nh>`, :doc:`fix langevin <fix_langevin>`,
+:doc:`pair_style srp <pair_srp>`, :doc:`fix mvv/dpd <fix_mvv_dpd>`.
 
 Default
 """""""

doc/src/pair_dpd_ext.rst

@@ -18,7 +18,6 @@ Accelerator Variants: dpd/ext/tstat/kk dpd/ext/tstat/omp
 Syntax
 """"""
 
-
 .. code-block:: LAMMPS
 
    pair_style dpd/ext T cutoff seed
@@ -32,16 +31,15 @@ Syntax
 Examples
 """"""""
 
-
 .. code-block:: LAMMPS
 
    pair_style dpd/ext 1.0 2.5 34387
    pair_coeff 1 1 25.0 4.5 4.5 0.5 0.5 1.2
    pair_coeff 1 2 40.0 4.5 4.5 0.5 0.5 1.2
 
-   pair_style dpd/ext/tstat 1.0 1.0 2.5 34387
+   pair_style hybrid/overlay lj/cut 2.5 dpd/ext/tstat 1.0 1.0 2.5 34387
-   pair_coeff 1 1 4.5 4.5 0.5 0.5 1.2
+   pair_coeff * * lj/cut 1.0 1.0
-   pair_coeff 1 2 4.5 4.5 0.5 0.5 1.2
+   pair_coeff * * 4.5 4.5 0.5 0.5 1.2
 
 Description
 """""""""""
@@ -128,20 +126,39 @@ the :doc:`pair_style <pair_style>` command so it does not need to be
 specified.
 
 For the style *dpd/ext/tstat*, the coefficients defined for each pair of
-atoms types via the :doc:`pair_coeff <pair_coeff>` command is the same,
+atoms types via the :doc:`pair_coeff <pair_coeff>` command are:
-except that A is not included.
+
+* :math:`\gamma_{\parallel}` (force/velocity units)
+* :math:`\gamma_{\perp}` (force/velocity units)
+* :math:`s_{\parallel}` (unitless)
+* :math:`s_{\perp}` (unitless)
+* :math:`r_c` (distance units)
+
+The last coefficient is optional.
 
 .. note::
 
    If you are modeling DPD polymer chains, you may want to use the
    :doc:`pair_style srp <pair_srp>` command in conjunction with these pair
-   styles. It is a soft segmental repulsive potential (SRP) that can
+   styles.  It is a soft segmental repulsive potential (SRP) that can
    prevent DPD polymer chains from crossing each other.
 
 .. note::
 
-   The virial calculation for pressure when using this pair style includes
+   The virial calculation for pressure when using these pair styles
-   all the components of force listed above, including the random force.
+   includes all the components of force listed above, including the
+   random force.  Since the random force depends on random numbers,
+   everything that changes the order of atoms in the neighbor list
+   (e.g. different number of MPI ranks or a different neighbor list
+   skin distance) will also change the sequence in which the random
+   numbers are applied and thus the individual forces and therefore
+   also the virial/pressure.
+
+.. note::
+
+   For more consistent time integration and force computation you may
+   consider using :doc:`fix mvv/dpd <fix_mvv_dpd>` instead of :doc:`fix
+   nve <fix_nve>`.
 
 ----------
 
@@ -207,7 +224,7 @@ Related commands
 
 :doc:`pair_style dpd <pair_dpd>`, :doc:`pair_coeff <pair_coeff>`,
 :doc:`fix nvt <fix_nh>`, :doc:`fix langevin <fix_langevin>`,
-:doc:`pair_style srp <pair_srp>`
+:doc:`pair_style srp <pair_srp>`, :doc:`fix mvv/dpd <fix_mvv_dpd>`.
 
 **Default:** none