81 lines
2.4 KiB
ReStructuredText
81 lines
2.4 KiB
ReStructuredText
.. index:: compute pressure/alchemy
|
|
|
|
compute pressure/alchemy command
|
|
================================
|
|
|
|
Syntax
|
|
""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
compute ID group-ID pressure/alchemy fix-ID
|
|
|
|
* ID, group-ID are documented in :doc:`compute <compute>` command
|
|
* pressure/alchemy = style name of this compute command
|
|
* fix-ID = ID of :doc:`fix alchemy <fix_alchemy>` command
|
|
|
|
Examples
|
|
""""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
fix trans all alchemy
|
|
compute mixed all pressure/alchemy trans
|
|
thermo_modify press mixed
|
|
|
|
Description
|
|
"""""""""""
|
|
|
|
.. versionadded:: 28Mar2023
|
|
|
|
Define a compute style that makes the "mixed" system pressure available
|
|
for a system that uses the :doc:`fix alchemy <fix_alchemy>` command to
|
|
transform one topology to another. This can be used in combination with
|
|
either :doc:`thermo_modify press <thermo_modify>` or :doc:`fix_modify
|
|
press <fix_modify>` to output and access a pressure consistent with the
|
|
simulated combined two topology system.
|
|
|
|
The actual pressure is determined with :doc:`compute pressure
|
|
<compute_pressure>` commands that are internally used by :doc:`fix
|
|
alchemy <fix_alchemy>` for each topology individually and then combined.
|
|
This command just extracts the information from the fix.
|
|
|
|
The ``examples/PACKAGES/alchemy`` folder contains an example input for this command.
|
|
|
|
----------
|
|
|
|
Output info
|
|
"""""""""""
|
|
|
|
This compute calculates a global scalar (the pressure) and a global
|
|
vector of length 6 (the pressure tensor), which can be accessed by
|
|
indices 1--6. These values can be used by any command that uses global
|
|
scalar or vector values from a compute as input. See the :doc:`Howto
|
|
output <Howto_output>` page for an overview of LAMMPS output options.
|
|
|
|
The ordering of values in the symmetric pressure tensor is as follows:
|
|
:math:`p_{xx},` :math:`p_{yy},` :math:`p_{zz},` :math:`p_{xy},`
|
|
:math:`p_{xz},` :math:`p_{yz}.`
|
|
|
|
The scalar and vector values calculated by this compute are "intensive".
|
|
The scalar and vector values will be in pressure :doc:`units <units>`.
|
|
|
|
Restrictions
|
|
""""""""""""
|
|
|
|
This compute is part of the REPLICA package. It is only enabled if
|
|
LAMMPS was built with that package. See the :doc:`Build package
|
|
<Build_package>` page for more info.
|
|
|
|
|
|
Related commands
|
|
""""""""""""""""
|
|
|
|
:doc:`fix alchemy <fix_alchemy>`, :doc:`compute pressure <compute_pressure>`,
|
|
:doc:`thermo_modify <thermo_modify>`, :doc:`fix_modify <fix_modify>`
|
|
|
|
Default
|
|
"""""""
|
|
|
|
none
|