.. _bsf:

[BSF]: Bloch spectral function
==============================

Parameters of the Bloch spectral function calculation.

.. tabularcolumns:: |\Yc{0.15}|\Yc{0.15}|\Yc{0.15}|\Yl{0.55}|

+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| Parameter          |  Type                 | Default     |  Description                                                |
+====================+=======================+=============+=============================================================+
| **e_range**        | `<energy>`            | [-1.0, 1.0] | Energy range: `e_min  e_max`                                |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| **n_points**       | `<integer>`           |     401     | Number of mesh points                                       |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| **im_delta**       | `<energy>`            |   0.03 Ry   | Small imaginary part                                        |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| **kset_params**    | `<block>`             |     NONE    | Parameters of the k-set                                     |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| **kpoints**        | `<string>`            |     NONE    | Type of coordinates: **frac** or **cart**                   |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
|                    | `<array>`             |     NONE    | Array of 3-vectors                                          |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
| **sections**       | `<string>`            |     NONE    | Type of coordinates: **frac** or **cart**                   |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+
|                    | `<sec def>`           |     NONE    | Definition of cross-sections for Fermi-surface calculations |
+--------------------+-----------------------+-------------+-------------------------------------------------------------+

-----

Block of **kset_params** defines the type of `k`-point set and default size parameters:

----

.. tabularcolumns:: |\Yc{0.15}|\Yc{0.2}|\Yc{0.1}|\Yl{0.55}|

+------------------+-----------------------+-------------+-------------------------------------------------------------+
| **type**         | `<string>`            |     NONE    | Type of the k-point set: **segments**, **sections**,        |
|                  |                       |             | **ibz**, **fbz**, **free**                                  |
+------------------+-----------------------+-------------+-------------------------------------------------------------+
| **segment_len**  | `<integer>`           |      30     | Length of a line segment when type is *segments*            |
+------------------+-----------------------+-------------+-------------------------------------------------------------+
| **section_size** | `<integer vector(2)>` |  [30, 30]   | Size of a section when type is *sections*                   |
+------------------+-----------------------+-------------+-------------------------------------------------------------+

----

If **type** is either **segments** or **free** the `k`-points will be read off the array in defined
by the **kpoints** block.

if **type** is **sections** the parameters of cross section will be taken from
the **sections** block defined as a set of lines starting with a label and followed by a set of parameters

----

+---------+----------------------------+
|  label  | <Cross-section parameters> |
+---------+----------------------------+

----

The label is given only for convenience as an annotation and must contain no white spaces.

Each cross-section represents a parallelogram in `k`-space, defined by a vertex point called **origin**
and two non-collinear vectors, **k1** and **k2**, defining the edges. The number of points along each
edge is either given by parameter **section_size**  in the **kset_params** section
or by an optional parameter **size** specified for each section separately.

----

.. tabularcolumns:: |\Yc{0.1}|\Yc{0.2}|\Yc{0.15}|\Yl{0.55}|

+--------------+-----------------------+-----------------+--------------------------------------+
| **origin**   | `<vector(3)>`         | [0.0, 0.0, 0.0] | Origin (vertex) point                |
+--------------+-----------------------+-----------------+--------------------------------------+
| **k1**       | `<vector(3)>`         |      NONE       | Edge vector **k1**                   |
+--------------+-----------------------+-----------------+--------------------------------------+
| **k2**       | `<vector(3)>`         |      NONE       | Edge vector **k2**                   |
+--------------+-----------------------+-----------------+--------------------------------------+
| **size**     | `<integer vector(2)>` |      NONE       | Number of points in the directions   |
|              |                       |                 | of **k1**, **k2**, respectively      |
+--------------+-----------------------+-----------------+--------------------------------------+

------

Notes:
******

    - square brackets for array values, `[val1, val2, ...]`, are used in the documentation
      for clarity and should not be used in the input file