git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14450 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp 2016-01-15 15:58:24 +00:00
parent 984a1afa72
commit 1174eacfbb
5 changed files with 52 additions and 15 deletions

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@ -170,7 +170,7 @@
<li>one or more keyword/value pairs may be appended</li>
</ul>
<pre class="literal-block">
keyword = <em>temp</em> or <em>iso</em> or <em>aniso</em> or <em>tri</em> or <em>x</em> or <em>y</em> or <em>z</em> or <em>xy</em> or <em>yz</em> or <em>xz</em> or <em>couple</em> or <em>tchain</em> or <em>pchain</em> or <em>mtk</em> or <em>tloop</em> or <em>ploop</em> or <em>nreset</em> or <em>drag</em> or <em>dilate</em> or <em>scalexy</em> or <em>scaleyz</em> or <em>scalexz</em> or <em>flip</em> or <em>fixedpoint</em>
keyword = <em>temp</em> or <em>iso</em> or <em>aniso</em> or <em>tri</em> or <em>x</em> or <em>y</em> or <em>z</em> or <em>xy</em> or <em>yz</em> or <em>xz</em> or <em>couple</em> or <em>tchain</em> or <em>pchain</em> or <em>mtk</em> or <em>tloop</em> or <em>ploop</em> or <em>nreset</em> or <em>drag</em> or <em>dilate</em> or <em>scalexy</em> or <em>scaleyz</em> or <em>scalexz</em> or <em>flip</em> or <em>fixedpoint</em> or <em>update</em>
<em>temp</em> values = Tstart Tstop Tdamp
Tstart,Tstop = external temperature at start/end of run
Tdamp = temperature damping parameter (time units)
@ -201,6 +201,7 @@ keyword = <em>temp</em> or <em>iso</em> or <em>aniso</em> or <em>tri</em> or <em
<em>flip</em> value = <em>yes</em> or <em>no</em> = allow or disallow box flips when it becomes highly skewed
<em>fixedpoint</em> values = x y z
x,y,z = perform barostat dilation/contraction around this point (distance units)
<em>update</em> value = <em>dipole</em> update dipole orientation (only for sphere variants)
</pre>
</div>
<div class="section" id="examples">
@ -235,12 +236,12 @@ correctly, the time-averaged temperature and stress tensor of the
particles will match the target values specified by Tstart/Tstop and
Pstart/Pstop.</p>
<p>The equations of motion used are those of Shinoda et al in
<a class="reference internal" href="pair_sdk.html#shinoda"><span>(Shinoda)</span></a>, which combine the hydrostatic equations of
Martyna, Tobias and Klein in <a class="reference internal" href="fix_rigid.html#martyna"><span>(Martyna)</span></a> with the strain
<a class="reference internal" href="#shinoda"><span>(Shinoda)</span></a>, which combine the hydrostatic equations of
Martyna, Tobias and Klein in <a class="reference internal" href="#martyna"><span>(Martyna)</span></a> with the strain
energy proposed by Parrinello and Rahman in
<a class="reference internal" href="fix_nh_eff.html#parrinello"><span>(Parrinello)</span></a>. The time integration schemes closely
<a class="reference internal" href="#parrinello"><span>(Parrinello)</span></a>. The time integration schemes closely
follow the time-reversible measure-preserving Verlet and rRESPA
integrators derived by Tuckerman et al in <a class="reference internal" href="run_style.html#tuckerman"><span>(Tuckerman)</span></a>.</p>
integrators derived by Tuckerman et al in <a class="reference internal" href="#tuckerman"><span>(Tuckerman)</span></a>.</p>
<hr class="docutils" />
<p>The thermostat parameters for fix styles <em>nvt</em> and <em>npt</em> is specified
using the <em>temp</em> keyword. Other thermostat-related keywords are
@ -397,7 +398,7 @@ freedom. A value of 0 corresponds to no thermostatting of the
barostat variables.</p>
<p>The <em>mtk</em> keyword controls whether or not the correction terms due to
Martyna, Tuckerman, and Klein are included in the equations of motion
<a class="reference internal" href="fix_rigid.html#martyna"><span>(Martyna)</span></a>. Specifying <em>no</em> reproduces the original
<a class="reference internal" href="#martyna"><span>(Martyna)</span></a>. Specifying <em>no</em> reproduces the original
Hoover barostat, whose volume probability distribution function
differs from the true NPT and NPH ensembles by a factor of 1/V. Hence
using <em>yes</em> is more correct, but in many cases the difference is
@ -406,7 +407,7 @@ negligible.</p>
scheme at little extra cost. The initial and final updates of the
thermostat variables are broken up into <em>tloop</em> substeps, each of
length <em>dt</em>/<em>tloop</em>. This corresponds to using a first-order
Suzuki-Yoshida scheme <a class="reference internal" href="run_style.html#tuckerman"><span>(Tuckerman)</span></a>. The keyword <em>ploop</em>
Suzuki-Yoshida scheme <a class="reference internal" href="#tuckerman"><span>(Tuckerman)</span></a>. The keyword <em>ploop</em>
does the same thing for the barostat thermostat.</p>
<p>The keyword <em>nreset</em> controls how often the reference dimensions used
to define the strain energy are reset. If this keyword is not used,
@ -447,6 +448,11 @@ to <em>fixedpoint</em>, then the lower periodic boundaries will remain at
far. In all cases, the particle trajectories are unaffected by the
chosen value, except for a time-dependent constant translation of
positions.</p>
<p>If the <em>update</em> keyword is used with the <em>dipole</em> value, then the
orientation of the dipole moment of each particle is also updated
during the time integration. This option should be used for models
where a dipole moment is assigned to finite-size particles,
e.g. spheroids via use of the <a class="reference internal" href="atom_style.html"><em>atom_style hybrid sphere dipole</em></a> command.</p>
<hr class="docutils" />
<div class="admonition note">
<p class="first admonition-title">Note</p>
@ -560,6 +566,18 @@ to undergo a slow random walk. This can be mitigated by resetting
the momentum at infrequent intervals using the
<a class="reference internal" href="fix_momentum.html"><em>fix momentum</em></a> command.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">This implementation has been shown to conserve linear momentum
up to machine precision under NVT dynamics. Under NPT dynamics,
for a system with zero initial total linear momentum, the total
momentum fluctuates close to zero. It may occasionally undergo brief
excursions to non-negligible values, before returning close to zero.
Over long simulations, this has the effect of causing the center-of-mass
to undergo a slow random walk. This can be mitigated by resetting
the momentum at infrequent intervals using the
<a class="reference internal" href="fix_momentum.html"><em>fix momentum</em></a> command.</p>
</div>
<hr class="docutils" />
<p>The fix npt and fix nph commands can be used with rigid bodies or
mixtures of rigid bodies and non-rigid particles (e.g. solvent). But

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@ -26,7 +26,7 @@ fix ID group-ID style_name keyword value ... :pre
ID, group-ID are documented in "fix"_fix.html command :ulb,l
style_name = {nvt} or {npt} or {nph} :l
one or more keyword/value pairs may be appended :l
keyword = {temp} or {iso} or {aniso} or {tri} or {x} or {y} or {z} or {xy} or {yz} or {xz} or {couple} or {tchain} or {pchain} or {mtk} or {tloop} or {ploop} or {nreset} or {drag} or {dilate} or {scalexy} or {scaleyz} or {scalexz} or {flip} or {fixedpoint}
keyword = {temp} or {iso} or {aniso} or {tri} or {x} or {y} or {z} or {xy} or {yz} or {xz} or {couple} or {tchain} or {pchain} or {mtk} or {tloop} or {ploop} or {nreset} or {drag} or {dilate} or {scalexy} or {scaleyz} or {scalexz} or {flip} or {fixedpoint} or {update}
{temp} values = Tstart Tstop Tdamp
Tstart,Tstop = external temperature at start/end of run
Tdamp = temperature damping parameter (time units)
@ -56,8 +56,9 @@ keyword = {temp} or {iso} or {aniso} or {tri} or {x} or {y} or {z} or {xy} or {y
{scalexz} value = {yes} or {no} = scale xz with lz
{flip} value = {yes} or {no} = allow or disallow box flips when it becomes highly skewed
{fixedpoint} values = x y z
x,y,z = perform barostat dilation/contraction around this point (distance units) :pre
x,y,z = perform barostat dilation/contraction around this point (distance units)
{update} value = {dipole} update dipole orientation (only for sphere variants) :pre
:ule
[Examples:]
@ -327,6 +328,13 @@ far. In all cases, the particle trajectories are unaffected by the
chosen value, except for a time-dependent constant translation of
positions.
If the {update} keyword is used with the {dipole} value, then the
orientation of the dipole moment of each particle is also updated
during the time integration. This option should be used for models
where a dipole moment is assigned to finite-size particles,
e.g. spheroids via use of the "atom_style hybrid sphere
dipole"_atom_style.html command.
:line
NOTE: Using a barostat coupled to tilt dimensions {xy}, {xz}, {yz} can
@ -450,6 +458,16 @@ to undergo a slow random walk. This can be mitigated by resetting
the momentum at infrequent intervals using the
"fix momentum"_fix_momentum.html command.
NOTE: This implementation has been shown to conserve linear momentum
up to machine precision under NVT dynamics. Under NPT dynamics,
for a system with zero initial total linear momentum, the total
momentum fluctuates close to zero. It may occasionally undergo brief
excursions to non-negligible values, before returning close to zero.
Over long simulations, this has the effect of causing the center-of-mass
to undergo a slow random walk. This can be mitigated by resetting
the momentum at infrequent intervals using the
"fix momentum"_fix_momentum.html command.
:line
The fix npt and fix nph commands can be used with rigid bodies or

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@ -163,8 +163,8 @@ assumes point particles and only updates their position and velocity.</p>
<p>If the <em>update</em> keyword is used with the <em>dipole</em> value, then the
orientation of the dipole moment of each particle is also updated
during the time integration. This option should be used for models
where a dipole moment is assigned to particles via use of the
<a class="reference internal" href="atom_style.html"><em>atom_style dipole</em></a> command.</p>
where a dipole moment is assigned to finite-size particles,
e.g. spheroids via use of the <a class="reference internal" href="atom_style.html"><em>atom_style hybrid sphere dipole</em></a> command.</p>
<hr class="docutils" />
<p>Styles with a <em>cuda</em>, <em>gpu</em>, <em>intel</em>, <em>kk</em>, <em>omp</em>, or <em>opt</em> suffix are
functionally the same as the corresponding style without the suffix.

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@ -39,8 +39,9 @@ assumes point particles and only updates their position and velocity.
If the {update} keyword is used with the {dipole} value, then the
orientation of the dipole moment of each particle is also updated
during the time integration. This option should be used for models
where a dipole moment is assigned to particles via use of the
"atom_style dipole"_atom_style.html command.
where a dipole moment is assigned to finite-size particles,
e.g. spheroids via use of the "atom_style hybrid sphere
dipole"_atom_style.html command.
:line

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