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.. module:: ase.calculators.gamess_us
=========
GAMESS-US
=========
`GAMESS-US <https://www.msg.chem.iastate.edu/gamess/index.html>`_ is a
computational chemistry software package based on gaussian basis functions.
Setup
=====
.. highlight:: bash
Ask your systems administrator to install GAMESS-US for you, or obtain
it yourself from the
`GAMESS-US download page <https://www.msg.chem.iastate.edu/gamess/download.html>`_.
Note that while GAMESS-US is available at no cost (including its source code),
it is not distributed under an open source license, thus you are not permitted
to redistribute copies of GAMESS-US or its source code.
GAMESS-US is distributed with a ``rungms`` script to run calculations. This
script must be customized for your computer or cluster. ASE expects that a
properly customized version of this ``rungms`` script will be present in your
``$PATH``. The default argument to run GAMESS-US in ASE is::
rungms PREFIX.inp > PREFIX.log 2> PREFIX.err
The default ``rungms`` script can be instructed to run across a number of CPU
cores through the following syntax::
rungms PREFIX.inp <VERSION> <NUMBER_OF_CORES> <CORES_PER_NODE> [<NUMBER_OF_NODES>]
For example, if you want to run a calculation on 8 cores, you might set the
``ASE_GAMESSUS_COMMAND`` environment variable to the following::
rungms PREFIX.inp 00 8 > PREFIX.log 2> PREFIX.err
Alternatively, this command can be passed as a string directly to the
``GAMESSUS`` Calculator with the ``command`` keyword argument.
Examples
========
Here is a command line example of how to optimize the geometry of a
water molecule using the PBE density functional::
$ ase build H2O | ase run gamess_us -p xc=PBE -f 0.02
$ ase gui stdin.traj@-1 -tg "a(1,0,2),d(0,1)"
102.59049267228833 1.0079388022627982
.. highlight:: python
An example of creating a GAMESS-US calculator using the python interface is::
from ase.calculators.gamess_us import GAMESSUS
calc = GAMESSUS(contrl=dict(scftyp='rhf', dfttyp='b3lyp', ispher=1),
dft=dict(dc=True, idcver=3),
basis=dict(gbasis='ccd'))
This will run a B3LYP/cc-pVDZ calculation with Stefan Grimme's DFT-D3
empirical dispersion correction.
Parameters
==========
.. highlight:: none
GAMESS-US organized keywords into blocks delimited by ``$<BLOCKNAME>`` and
``$END``. The ``GAMESSUS`` calculator represents these blocks as dictionaries.
For example, consider the following block of input::
$CONTRL SCFTYP=RHF DFTTYP=M06 $END
$SYSTEM MWORDS=4 $END
$BASIS
GBASIS=N31
NGAUSS=6
NDFUNC=1
$END
$DFT NRAD=96 NLEB=1202 $END
.. highlight:: python
Note that keywords within a block can be on the same or different lines.
Equivalent input will be generated by invoking the ``GAMESSUS`` calculator
with the following arguments::
calc = GAMESSUS(contrl=dict(scftyp='rhf', dfttyp='m06'),
system=dict(mwords=4),
basis=dict(gbasis='n31', ngauss=6, ndfunc=1),
dft=dict(nrad=96, nleb=1202))
.. highlight:: none
Note that though GAMESS-US is case insensitive, Python is case sensitive.
The ``GAMESSUS`` calculator expects lowercase keywords.
Most input files can be constructed in this way. The ``GAMESSUS`` calculator also
has several special keywords, which are described in the table below
============== ======== ================ ==================================================
keyword type default value description
============== ======== ================ ==================================================
``label`` ``str`` ``'gamess_us'`` Used to name input and output files.
``userscr`` ``str`` ``None`` The ``USERSCR`` directory defined in ``rungms``.
If not provided, ASE will attempt to automatically
determine the correct value from your ``rungms``
script. This is not guaranteed to work, in which case
you will need to manually provide the proper location.
``basis`` ``dict`` See description Specifies the arguments that go into the ``$BASIS``
block in the GAMESS-US input file. Defaults to
``{'gbasis': 'n21', 'ngauss': 3}``, i.e. 3-21G.
Alternately, ``basis`` accepts a dictionary of
literal basis set definitions where the keys
correspond to element type or atom index.
``ecp`` ``dict`` ``None`` A dictionary of literal ECP definitions. Keys should
be either an element symbol or an atom index.
============== ======== ================ ==================================================
.. autoclass:: GAMESSUS
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