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User's guide

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Anthony Scemama 2018-10-23 23:43:28 +02:00
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docs/source/users_guide.rst
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@ -5,10 +5,10 @@ The input data is stored in a `EZFIO`_ database. It is a hierarchical data
format which uses the hierarchy of the file system to organize the data, stored
in a directory.
To access the data in the EZFIO file, you can use the provided API (Fortran,
Python, OCaml or bash), or tools such as `qp_edit` provided with the Quantum
Python, OCaml or Bash), or tools such as ``qp_edit`` provided with the Quantum
Package. The data in the EZFIO directory is stroed as plain text files, so
it can be read with a text editor.
To create an EZFIO directory from scratch, the `qp_create_ezfio_from_xyz` should
To create an EZFIO directory from scratch, the ``qp_create_ezfio_from_xyz`` should
be used.
qp_create_ezfio_from_xyz
@ -28,8 +28,6 @@ Flags ::
[-m int] Spin multiplicity (2S+1) of the molecule. Default is 1.
[-o file] Name of the created EZFIO file.
[-p string] Name of the pseudopotential
[-build-info] print info about this build and exit
[-version] print the version of this build and exit
[-help] print this help text and exit
(alias: -?)
@ -54,7 +52,7 @@ qp_set_mo_class
Usage ::
qp_set_mo_class EZFIO_DIRECTORY
qp_set_mo_class [FLAGS] EZFIO_DIRECTORY
Flags ::
@ -65,8 +63,6 @@ Flags ::
[-inact range] Range of inactive orbitals
[-q] Query: print the current masks
[-virt range] Range of virtual orbitals
[-build-info] print info about this build and exit
[-version] print the version of this build and exit
[-help] print this help text and exit
(alias: -?)
@ -89,9 +85,9 @@ Virtual
To avoid errors, all the MOs should be given a class.
The range of MOs are given like the ranges in SLURM commands. For example,
`"[36-53,72-107,126-131]"`.
``"[36-53,72-107,126-131]"``.
To quickly setup a frozen core calculation, the script `qp_set_frozen_core.py`
To quickly setup a frozen core calculation, the script ``qp_set_frozen_core.py``
can be used::
qp_set_frozen_core.py EZFIO_DIRECTORY
@ -108,21 +104,26 @@ Excited states
--------------
It is possible to run excited states calculations with the quantum package. To
do this, set the `n_states` variable in the `Determinants` section to the
do this, set the ``n_states`` variable in the ``Determinants`` section to the
number of requested states. The selection criterion will be the maximum of the
selection criteria for each state. If the Davidson diagonalization has
difficulties to converge, increase the `n_states_diag` variable in the
`Davidson` section.
difficulties to converge, increase the ``n_states_diag`` variable in the
``Davidson`` section.
When computing multiple states, it is good to have the `s2_eig` flag of the
`Determinants` section set to `true`. This will force the Davidson algorithm to
When computing multiple states, it is good to have the ``s2_eig`` flag of the
``Determinants`` section set to ``true``. This will force the Davidson algorithm to
choose only vectors with a value of S^2 equal to the ``expected_s2``.
Otherwise, different spin states will come out in the diagonalization.
The Quantum Package doesn't take account of the symmetry. Due to numerical
noise, excited states of different symmetries may enter in the calculation.
Note that it is possible to make state-average calculation of states with
different symmetries and/or different spin multiplicities.
To include excited state of all possible symmetries, a simple trick is to
run a preliminary multi-state CIS calculation, and then running the selected
FCI restarting from the CIS states, setting the `read_wf` flag of the
`Determinants` section tp `true`.
FCI restarting from the CIS states, setting the ``read_wf`` flag of the
``Determinants`` section to ``true``.
Usually, it is good practice to use state-averaged MOs so that all states have
MOs of comparable quality. For example, when searching for a singly excited
@ -134,22 +135,13 @@ calculation.
Natural orbitals
----------------
To produce state-average natural orbitals, run
To produce state-average natural orbitals, run ::
```
qp_run save_natorb file.ezfio
```
qp_run save_natorb file.ezfio
The MOs will be replaced, so the two-electron integrals and the wave function are invalidated as well.
The QP doesn't take account of the symmetry. For reasons due to numerical noise,
excited states of different symmetries may enter in the calculation.
Note that it is possible to make state-average calculation of states with different
symmetries and/or different spin multiplicities.
.. _EZFIO: http://gitlab.com/scemama/EZFIO