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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@2614 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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2009-03-03 17:00:10 +00:00
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36
doc/compute_pressure.html
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@ -47,21 +47,24 @@ and long-range interactions. <A HREF = "fix.html">Fixes</A> that impose constra
(e.g. the <A HREF = "fix_shake.html">fix shake</A> command) also contribute to the
virial term.
</P>
<P>A 6-component pressure tensor is also calculated by this compute whose
components can be output by the <A HREF = "thermo_style.html">thermo_style
<P>A 6-component symmetric pressure tensor is also calculated by this
compute whose components can be output by the <A HREF = "thermo_style.html">thermo_style
custom</A> command or accessed by other
<A HREF = "compute.html">compute</A> and <A HREF = "fix.html">fix</A> commands. The equation for
the components of the tensor is the same as in above formula, except
that the first term uses the components of the kinetic energy tensor
(vx * vy instead of v^2 for temperature) and the second term uses Rx *
Fy for the Wxy component of the virial tensor, etc.
<A HREF = "compute.html">compute</A> and <A HREF = "fix.html">fix</A> commands. The 6 values are
1 = Pxx, 2 = Pyy, 3 = Pzz, 4 = Pxy, 5 = Pxz, 6 = Pyz. The equation
for the I,J components (where I and J = x,y,z) is similar to the above
formula, except that the first term uses components of the kinetic
energy tensor and the second term uses components of the virial
tensor:
</P>
<P>If no extra keywords are listed, the entire equation above is
calculated which includes a temperature term (or kinetic energy
tensor) and the virial as the sum of pair, bond, angle, dihedral,
improper, kspace (long-range), and fix contributions. If any extra
keywords are listed, then only those components are summed to compute
ke and/or the virial.
<CENTER><IMG SRC = "Eqs/pressure_tensor.jpg">
</CENTER>
<P>If no extra keywords are listed, the entire equations above are
calculated which include a temperature (or kinetic energy) term and
the virial as the sum of pair, bond, angle, dihedral, improper, kspace
(long-range), and fix contributions to the force on each atom. If any
extra keywords are listed, then only those components are summed to
compute temperature or ke and/or the virial.
</P>
<P>The temperature and kinetic energy tensor is not calculated by this
compute, but rather by the temperature compute specified with the
@ -70,9 +73,10 @@ all atoms for consistency with the virial term, but any compute style
that calculates temperature can be used, e.g. one that excludes frozen
atoms or other degrees of freedom.
</P>
<P>Note that the N is the above formula is really degrees-of-freedom
where the DOF is specified by the temperature compute. See the
various <A HREF = "compute.html">compute temperature</A> styles for details.
<P>Note that the N in the first formula above is really
degrees-of-freedom divided by 3, where the DOF is calcluated by the
temperature compute. See the various <A HREF = "compute.html">compute
temperature</A> styles for details.
</P>
<P>A compute of this style with the ID of "thermo_press" is created when
LAMMPS starts up, as if this command were in the input script:

36
doc/compute_pressure.txt
View File

@ -44,21 +44,24 @@ and long-range interactions. "Fixes"_fix.html that impose constraints
(e.g. the "fix shake"_fix_shake.html command) also contribute to the
virial term.
A 6-component pressure tensor is also calculated by this compute whose
components can be output by the "thermo_style
A 6-component symmetric pressure tensor is also calculated by this
compute whose components can be output by the "thermo_style
custom"_thermo_style.html command or accessed by other
"compute"_compute.html and "fix"_fix.html commands. The equation for
the components of the tensor is the same as in above formula, except
that the first term uses the components of the kinetic energy tensor
(vx * vy instead of v^2 for temperature) and the second term uses Rx *
Fy for the Wxy component of the virial tensor, etc.
"compute"_compute.html and "fix"_fix.html commands. The 6 values are
1 = Pxx, 2 = Pyy, 3 = Pzz, 4 = Pxy, 5 = Pxz, 6 = Pyz. The equation
for the I,J components (where I and J = x,y,z) is similar to the above
formula, except that the first term uses components of the kinetic
energy tensor and the second term uses components of the virial
tensor:
If no extra keywords are listed, the entire equation above is
calculated which includes a temperature term (or kinetic energy
tensor) and the virial as the sum of pair, bond, angle, dihedral,
improper, kspace (long-range), and fix contributions. If any extra
keywords are listed, then only those components are summed to compute
ke and/or the virial.
:c,image(Eqs/pressure_tensor.jpg)
If no extra keywords are listed, the entire equations above are
calculated which include a temperature (or kinetic energy) term and
the virial as the sum of pair, bond, angle, dihedral, improper, kspace
(long-range), and fix contributions to the force on each atom. If any
extra keywords are listed, then only those components are summed to
compute temperature or ke and/or the virial.
The temperature and kinetic energy tensor is not calculated by this
compute, but rather by the temperature compute specified with the
@ -67,9 +70,10 @@ all atoms for consistency with the virial term, but any compute style
that calculates temperature can be used, e.g. one that excludes frozen
atoms or other degrees of freedom.
Note that the N is the above formula is really degrees-of-freedom
where the DOF is specified by the temperature compute. See the
various "compute temperature"_compute.html styles for details.
Note that the N in the first formula above is really
degrees-of-freedom divided by 3, where the DOF is calcluated by the
temperature compute. See the various "compute
temperature"_compute.html styles for details.
A compute of this style with the ID of "thermo_press" is created when
LAMMPS starts up, as if this command were in the input script: