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===========
QCElemental
===========

*QCElemental is a resource module for quantum chemistry (QC) containing physical
constants and periodic table data from NIST. It also contains molecule handlers
(suitable for QC parsing and input files) and the QC data exchange format known
as QCSchema.*

Physical Constants
------------------

Physical constants can be acquired directly from the NIST CODATA:

.. code-block:: python

    >>> qcel.constants.get("hartree energy in ev")
    27.21138602

Alternatively, with the use of the Pint unit conversion package, arbitrary
conversion factors can be obtained:

.. code-block:: python

    >>> qcel.constants.conversion_factor("bohr", "miles")
    3.2881547429884475e-14

Periodic Table Data
-------------------

A variety of periodic table quantities are available using virtually any alias:

.. code-block:: python

    >>> qcel.periodictable.to_mass("Ne")
    19.9924401762

    >>> qcel.periodictable.to_mass(10)
    19.9924401762

Molecule Handlers
-----------------

Molecules can be translated to/from the `MolSSI QCSchema
<https://github.com/MolSSI/QCSchema>`_ format or quantum chemistry
program specific input specifications such as NWChem, Psi4, and CFour. In
addition, databases such as PubChem can be searched:

.. code-block:: python

    >>> qcel.molparse.from_string("pubchem:benzene")
        Searching PubChem database for benzene (single best match returned)
        Found 1 result(s)
        {"geometry": ...}

========

Index
-----

**Getting Started**

* :doc:`install`

.. toctree::
   :maxdepth: 1
   :hidden:
   :caption: Getting Started

   install

**QCSchema Models**

Implementation descriptions of QCSchema objects in Python.

* :doc:`models`
* :doc:`model_molecule`
* :doc:`model_result`
* :doc:`model_opt`
* :doc:`model_common`

.. toctree::
   :maxdepth: 1
   :hidden:
   :caption: QCSchema Models

   models
   model_molecule
   model_result
   model_opt
   model_td
   model_common

**Quantities**

* :doc:`physconst`
* :doc:`periodic_table`
* :doc:`covalent_radii`
* :doc:`vanderwaals_radii`

.. toctree::
   :maxdepth: 1
   :hidden:
   :caption: Quantities

   physconst
   periodic_table
   covalent_radii
   vanderwaals_radii

**Developer Documentation**

Contains in-depth developer documentation and API references.

* :doc:`api`
* :doc:`changelog`

.. toctree::
   :maxdepth: 2
   :caption: Developer Documentation
   :hidden:

   api
   changelog


Indices and tables
==================

* :ref:`genindex`
* :ref:`modindex`
* :ref:`search`