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rLAMMPS lammps
thermo_style.html
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<HTML>
<CENTER><A
HREF =
"http://lammps.sandia.gov"
>
LAMMPS WWW Site
</A>
-
<A
HREF =
"Manual.html"
>
LAMMPS Documentation
</A>
-
<A
HREF =
"Section_commands.html#comm"
>
LAMMPS Commands
</A>
</CENTER>
<HR>
<H3>
thermo_style command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
thermo_style style args
</PRE>
<UL><LI>
style =
<I>
one
</I>
or
<I>
multi
</I>
or
<I>
custom
</I>
<LI>
args = list of arguments for a particular style
<PRE>
<I>
one
</I>
args = none
<I>
multi
</I>
args = none
<I>
custom
</I>
args = list of attributes
possible attributes = step, atoms, cpu, temp, press,
pe, ke, etotal, enthalpy,
evdwl, ecoul, epair, ebond, eangle, edihed, eimp,
emol, elong, etail,
vol, lx, ly, lz, xlo, xhi, ylo, yhi, zlo, zhi,
pxx, pyy, pzz, pxy, pxz, pyz
c_ID, c_ID[n], f_ID, f_ID[n], v_name
step = timestep
atoms = # of atoms
cpu = elapsed CPU time
temp = temperature
press = pressure
pe = total potential energy
ke = kinetic energy
etotal = total energy (pe + ke)
enthalpy = enthalpy (pe + press*vol)
evdwl = VanderWaal pairwise energy
ecoul = Coulombic pairwise energy
epair = pairwise energy (evdwl + ecoul + elong + etail)
ebond = bond energy
eangle = angle energy
edihed = dihedral energy
eimp = improper energy
emol = molecular energy (ebond + eangle + edihed + eimp)
elong = long-range kspace energy
etail = VanderWaal energy long-range tail correction
vol = volume
lx,ly,lz = box lengths in x,y,z
xlo,xhi,ylo,yhi,zlo,zhi = box boundaries
pxx,pyy,pzz,pxy,pxz,pyz = 6 components of pressure tensor
c_ID = global scalar value calculated by a compute with ID
c_ID[N] = Nth component of global vector calculated by a compute with ID
f_ID = global scalar value calculated by a fix with ID
f_ID[N] = Nth component of global vector calculated by a fix with ID
v_name = global value calculated by an equal-style variable with name
</PRE>
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
thermo_style multi
thermo_style custom step temp pe etotal press vol
thermo_style custom step temp etotal c_myTemp v_abc
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Set the style and content for printing thermodynamic data to the
screen and log file.
</P>
<P>
Style
<I>
one
</I>
prints a one-line summary of thermodynamic info that is
the equivalent of "thermo_style custom step temp epair emol etotal
press". The line contains only numeric values.
</P>
<P>
Style
<I>
multi
</I>
prints a multiple-line listing of thermodynamic info
that is the equivalent of "thermo_style custom etotal ke temp pe ebond
eangle edihed eimp evdwl ecoul elong press". The listing contains
numeric values and a string ID for each quantity.
</P>
<P>
Style
<I>
custom
</I>
is the most general setting and allows you to specify
which of the keywords listed above you want printed on each
thermodynamic timestep. Note that the keywords c_ID, f_ID, v_name are
references to
<A
HREF =
"compute.html"
>
computes
</A>
,
<A
HREF =
"fix.html"
>
fixes
</A>
, and
equal-style
<A
HREF =
"variable.html"
"
>
variables
</A>
that have been defined
elsewhere in the input script or can even be new styles which users
have added to LAMMPS (see the
<A
HREF =
"Section_modify.html"
>
Section_modify
</A>
section of the documentation). Thus the
<I>
custom
</I>
style provides a
flexible means of outputting essentially any desired quantity as a
simulation proceeds.
</P>
<P>
All styles except
<I>
custom
</I>
have
<I>
vol
</I>
appended to their list of
outputs if the simulation box volume changes during the simulation.
</P>
<P>
The values printed by the various keywords are instantaneous values,
calculated on the current timestep. Time-averaged quantities, which
include values from previous timesteps, can be output by using the
f_ID keyword and accessing a fix that does time-averaging such as the
<A
HREF =
"fix_ave_time.html"
>
fix ave/time
</A>
command.
</P>
<P>
Options invoked by the
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
command can
be used to set the one- or multi-line format of the print-out, the
normalization of thermodynamic output (total values versus per-atom
values for "extensive quantities, meaning ones which scale with the
number of atoms in the system), and the numeric precision of each
printed value.
</P>
<P>
IMPORTANT NOTE: When you use a "thermo_style" command, all
thermodynamic settings are restored to their default values, including
those previously set by a
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
command.
Thus if your input script specifies a thermo_style command, you should
use the thermo_modify command after it.
</P>
<HR>
<P>
Several of the thermodynamic quantities require a temperature to be
computed: "temp", "press", "ke", "etotal", "enthalpy", "pxx etc". By
default this is done by using the "thermo_temp" compute which is
created when LAMMPS starts up, as if this command had been issued:
</P>
<PRE>
compute thermo_temp all temp
</PRE>
<P>
See the
<A
HREF =
"compute_temp.html"
>
compute temp
</A>
command for details. Note
that the ID of this compute is
<I>
thermo_temp
</I>
and the group is
<I>
all
</I>
.
You can change the attributes of this temperature (e.g. its
degrees-of-freedom) via the
<A
HREF =
"compute_modify.html"
>
compute_modify
</A>
command. Alternatively, you can directly assign a new compute (that
calculates temperature) which you have defined, to be used for
calculating any thermodynamic quantity that requires a temperature.
This is done via the
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
command.
</P>
<P>
Several of the thermodynamic quantities require a pressure to be
computed: "press", "enthalpy", "pxx", etc. By default this is done by
using the pressure compute which is created when LAMMPS starts up, as
if this command had been issued:
</P>
<PRE>
compute thermo_press all pressure thermo_temp
</PRE>
<P>
See the
<A
HREF =
"compute_pressure.html"
>
compute pressure
</A>
command for details.
Note that the ID of this compute is
<I>
thermo_press
</I>
and the group is
<I>
all
</I>
. You can change the attributes of this pressure via the
<A
HREF =
"compute_modify.html"
>
compute_modify
</A>
command. Alternatively, you can
directly assign a new compute (that calculates pressure) which you
have defined, to be used for calculating any thermodynamic quantity
that requires a pressure. This is done via the
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
command.
</P>
<P>
Several of the thermodynamic quantities require a potential energy to
be computed: "pe", "etotal", "ebond", etc. This is done by using the
"thermo_pe" compute which is created when LAMMPS starts up, as if this
command had been issued:
</P>
<PRE>
compute thermo_pe all pe
</PRE>
<P>
See the
<A
HREF =
"compute_pe.html"
>
compute pe
</A>
command for details. Note that
the ID of this compute is
<I>
thermo_pe
</I>
and the group is
<I>
all
</I>
. You can
change the attributes of this potential energy via the
<A
HREF =
"compute_modify.html"
>
compute_modify
</A>
command.
</P>
<HR>
<P>
The kinetic energy of the system
<I>
ke
</I>
is inferred from the temperature
of the system with 1/2 Kb T of energy for each degree of freedom.
Thus, using different
<A
HREF =
"compute.html"
>
compute commands
</A>
for calculating
temperature, via the
<A
HREF =
"thermo_modify.html"
>
thermo_modify temp
</A>
command,
may yield different kinetic energies, since different computes that
calculate temperature can subtract out different non-thermal
components of velocity and/or include different degrees of freedom
(translational, rotational, etc).
</P>
<P>
The potential energy of the system
<I>
pe
</I>
will include contributions
from fixes if the
<A
HREF =
"fix_modify.html"
>
fix_modify thermo
</A>
option is set
for a fix that calculates such a contribution. For example, the
<A
HREF =
"fix_wall_lj93"
>
fix
wall/lj93
</A>
fix calculates the energy of atoms
interacting with the wall. See the doc pages for "individual fixes"
to see which ones contribute.
</P>
<P>
A long-range tail correction
<I>
etail
</I>
for the VanderWaal pairwise
energy will be non-zero only if the
<A
HREF =
"pair_modify.html"
>
pair_modify
tail
</A>
option is turned on. The
<I>
etail
</I>
contribution
is included in
<I>
evdwl
</I>
,
<I>
pe
</I>
, and
<I>
etotal
</I>
, and the corresponding tail
correction to the pressure is included in
<I>
press
</I>
and
<I>
pxx
</I>
,
<I>
pyy
</I>
,
etc.
</P>
<HR>
<P>
The
<I>
c_ID
</I>
and
<I>
c_ID[N]
</I>
keywords allow global scalar or vector
quantities calculated by a compute to be output. The ID in the
keyword should be replaced by the actual ID of the compute that has
been defined elsewhere in the input script. See the
<A
HREF =
"compute.html"
>
compute
</A>
command for details. Note that only global
scalar or vector quantities calculated by a compute can be output as
thermodynamic data; per-atom quantities calculated by a compute can be
output by the
<A
HREF =
"dump.html"
>
dump custom
</A>
command. There is a
<A
HREF =
"compute_reduce.html"
>
compute
reduce
</A>
command which can sum per-atom quantities
into a global scalar or vector which can be output by thermo_style
custom.
</P>
<P>
Note that some computes calculate "intensive" global quantities like
temperature; others calculate "extensive" global quantities like
kinetic energy that are summed over all atoms in the compute group.
Intensive quantities are printed directly as is by thermo_style
custom. Extensive quantities may be normalized when output by the
total number of atoms in the simulation (NOT the number of atoms in
the compute group) depending on the
<A
HREF =
"thermo_modify.html"
>
thermo_modify
norm
</A>
option being used.
</P>
<P>
If
<I>
c_ID
</I>
is used as a keyword, then the scalar quantity calculated by
the compute is printed. If
<I>
c_ID[N]
</I>
is used, then N must be an
index from 1-M where M is the length of the vector calculated by the
compute. See the doc pages for individual compute styles for info on
what these quantities are.
</P>
<P>
The
<I>
f_ID
</I>
and
<I>
f_ID[N]
</I>
keywords allow global scalar or vector
quantities calculated by a fix to be output. The ID in the keyword
should be replaced by the actual ID of the fix that has been defined
elsewhere in the input script. See the doc pages for individual
<A
HREF =
"fix.html"
>
fix
commands
</A>
for details of which fixes generate global values.
One particularly useful fix to use in this context is the
<A
HREF =
"fix_ave_time.html"
>
fix
ave/time
</A>
command, which calculates time-averages of
global scalar and vector quantities calculated by other
<A
HREF =
"compute.html"
>
computes
</A>
,
<A
HREF =
"fix.html"
>
fixes
</A>
, or
<A
HREF =
"variable.html"
>
variables
</A>
.
</P>
<P>
Note that some fixes calculate "intensive" global quantities like
timestep size; others calculate "extensive" global quantities like
energy that are summed over all atoms in the fix group. Intensive
quantities are printed directly as is by thermo_style custom.
Extensive quantities may be normalized when output by the total number
of atoms in the simulation (NOT the number of atoms in the fix group)
depending on the
<A
HREF =
"thermo_modify.html"
>
thermo_modify norm
</A>
option being
used.
</P>
<P>
If
<I>
f_ID
</I>
is used as a keyword, then the scalar quantity calculated by
the fix is printed. If
<I>
f_ID[N]
</I>
is used, then N must be an index
from 1-M where M is the length of the vector calculated by the fix.
See the doc pages for individual fix styles for info on which fixes
calculate these global quantities and what they are. For fixes that
compute a contribution to the potential energy of the system, the
scalar quantity referenced by f_ID is typically that quantity.
</P>
<P>
The
<I>
v_name
</I>
keyword allow the current value of a variable to be
output. The name in the keyword should be replaced by the actual name
of the variable that has been defined elsewhere in the input script.
Only equal-style variables can be referenced. See the
<A
HREF =
"variable.html"
>
variable
</A>
command for details. Variables of style
<I>
equal
</I>
can reference individual atom properties or thermodynamic
keywords, or they can invoke other computes, fixes, or variables when
evaluated, so this is a very general means of creating thermodynamic
output.
</P>
<P>
See
<A
HREF =
"Section_modify.html"
>
this section
</A>
for information on how to add
new compute and fix styles to LAMMPS to calculate quantities that
could then be output with these keywords as part of thermodynamic
information.
</P>
<HR>
<P><B>
Restrictions:
</B>
</P>
<P>
This command must come after the simulation box is defined by a
<A
HREF =
"read_data.html"
>
read_data
</A>
,
<A
HREF =
"read_restart.html"
>
read_restart
</A>
, or
<A
HREF =
"create_box.html"
>
create_box
</A>
command.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"thermo.html"
>
thermo
</A>
,
<A
HREF =
"thermo_modify.html"
>
thermo_modify
</A>
,
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
,
<A
HREF =
"compute_temp.html"
>
compute temp
</A>
,
<A
HREF =
"compute_pressure.html"
>
compute pressure
</A>
</P>
<P><B>
Default:
</B>
</P>
<PRE>
thermo_style one
</PRE>
</HTML>
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