These are compute styles contributed by users, which can be used if diff --git a/doc/Section_commands.txt b/doc/Section_commands.txt index 4db4b624c1..409ff31ad1 100644 --- a/doc/Section_commands.txt +++ b/doc/Section_commands.txt @@ -452,6 +452,7 @@ description: "stress/atom"_compute_stress_atom.html, "temp"_compute_temp.html, "temp/asphere"_compute_temp_asphere.html, +"temp/com"_compute_temp_com.html, "temp/deform"_compute_temp_deform.html, "temp/dipole"_compute_temp_dipole.html, "temp/partial"_compute_temp_partial.html, diff --git a/doc/compute.html b/doc/compute.html index 8285934ce8..ee4a2d7e3e 100644 --- a/doc/compute.html +++ b/doc/compute.html @@ -123,6 +123,7 @@ available in LAMMPS:
Syntax: +
+compute ID group-ID temp/com ++
Examples: +
+compute 1 all temp/com +compute myTemp mobile temp/com ++
Description: +
+Define a computation that calculates the temperature of a group of +atoms, after subtracting out the center-of-mass velocity of the group. +This is useful if the group is expected to have a non-zero net +velocity for some reason. A compute of this style can be used by any +command that computes a temperature, +e.g. thermo_modify, fix +temp/rescale, fix npt, etc. +
+The temperature is calculated by the formula KE = dim/2 N k T, where +KE = total kinetic energy of the group of atoms (sum of 1/2 m v^2), +dim = 2 or 3 = dimensionality of the simulation, N = number of atoms +in the group, k = Boltzmann constant, and T = temperature. +
+A 6-component kinetic energy tensor is also calculated by this compute +for use in the computation of a pressure tensor. The formula for the +components of the tensor is the same as the above formula, except that +v^2 is replaced by vx * vy for the xy component, etc. +
+The number of atoms contributing to the temperature is assumed to be +constant for the duration of the run; use the dynamic option of the +compute_modify command if this is not the case. +
+This compute subtracts out degrees-of-freedom due to fixes that +constrain molecular motion, such as fix shake and +fix rigid. This means the temperature of groups of +atoms that include these constraints will be computed correctly. If +needed, the subtracted degrees-of-freedom can be altered using the +extra option of the compute_modify command. +
+Output info: +
+The scalar value calculated by this compute is "intensive", meaning it +is independent of the number of atoms in the simulation. The vector +values are "extensive", meaning they scale with the number of atoms in +the simulation. +
+Restrictions: none +
+Related commands: +
+ +Default: none +
+ diff --git a/doc/compute_temp_com.txt b/doc/compute_temp_com.txt new file mode 100644 index 0000000000..56c6a0584a --- /dev/null +++ b/doc/compute_temp_com.txt @@ -0,0 +1,67 @@ +"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c + +:link(lws,http://lammps.sandia.gov) +:link(ld,Manual.html) +:link(lc,Section_commands.html#comm) + +:line + +compute temp/com command :h3 + +[Syntax:] + +compute ID group-ID temp/com :pre + +ID, group-ID are documented in "compute"_compute.html command +temp/com = style name of this compute command :ul + +[Examples:] + +compute 1 all temp/com +compute myTemp mobile temp/com :pre + +[Description:] + +Define a computation that calculates the temperature of a group of +atoms, after subtracting out the center-of-mass velocity of the group. +This is useful if the group is expected to have a non-zero net +velocity for some reason. A compute of this style can be used by any +command that computes a temperature, +e.g. "thermo_modify"_thermo_modify.html, "fix +temp/rescale"_fix_temp_rescale.html, "fix npt"_fix_npt.html, etc. + +The temperature is calculated by the formula KE = dim/2 N k T, where +KE = total kinetic energy of the group of atoms (sum of 1/2 m v^2), +dim = 2 or 3 = dimensionality of the simulation, N = number of atoms +in the group, k = Boltzmann constant, and T = temperature. + +A 6-component kinetic energy tensor is also calculated by this compute +for use in the computation of a pressure tensor. The formula for the +components of the tensor is the same as the above formula, except that +v^2 is replaced by vx * vy for the xy component, etc. + +The number of atoms contributing to the temperature is assumed to be +constant for the duration of the run; use the {dynamic} option of the +"compute_modify"_compute_modify.html command if this is not the case. + +This compute subtracts out degrees-of-freedom due to fixes that +constrain molecular motion, such as "fix shake"_fix_shake.html and +"fix rigid"_fix_rigid.html. This means the temperature of groups of +atoms that include these constraints will be computed correctly. If +needed, the subtracted degrees-of-freedom can be altered using the +{extra} option of the "compute_modify"_compute_modify.html command. + +[Output info:] + +The scalar value calculated by this compute is "intensive", meaning it +is independent of the number of atoms in the simulation. The vector +values are "extensive", meaning they scale with the number of atoms in +the simulation. + +[Restrictions:] none + +[Related commands:] + +"compute temp"_compute_temp.html + +[Default:] none