Structure

Element: structure

This element contains all structural information, such as unit-cell parameters as well as type and position of each atom. The presence of the subelement species is necessary unless one wants to perform an empty-lattice calculation. The attribute speciespath must be specified.

contains: crystal (required)
species (optional)
XPath: /input/structure

This element allows for specification of the following attributes: speciespath (required), autormt, epslat, molecule, primcell, rmtapm, tshift, vacuum

Attribute: autormt

If "true", the muffin-tin radius of each species is automatically set according to the variables specified by the attribute rmtapm.

Type: boolean
Default: "false"
Use: optional
XPath: /input/structure/@autormt


Attribute: epslat

This attribute defines the accuracy up to which two vectors can be considered numerically identical. Vectors with lengths less than this are considered zero.

Type: fortrandouble
Default: "1.0d-6"
Use: optional
Unit: Bohr
XPath: /input/structure/@epslat


Attribute: molecule

If "true", a calculation for an isolated molecule is performed. In this case, the atomic positions specified by the atom subelement of the species element must be given in cartesian coordinates. The lattice vectors are set up automatically as

(1)
\begin{align} {\bf A}^{(i)}=A_i\,\,\hat{\bf e}^{(i)} \qquad i=1,2,3 \end{align}

with

(2)
\begin{align} A_i=\max_{\alpha,\beta}\left|{ a}^{(\alpha)}_i-{a}^{(\beta)}_i\right| +d_{\rm vac} \end{align}

where ${a}_i^{(\alpha)}$ is the catesian component of the atom labeled by $\alpha$ in the $i$-th direction specified by the unit vector $\hat{\bf e}^{(i)}$. Furthermore, $d_{\rm vac}$ represents the size of the vacuum around the molecule as defined by the attribute vacuum.

Type: boolean
Default: "false"
Use: optional
XPath: /input/structure/@molecule


Attribute: primcell

If "true", the primitive unit cell is determined automatically from the conventional cell defined by the basis vectors given by the basevect elements. The primitive unit cell is determined by searching for lattice vectors among all vectors connecting atomic sites and choosing the three shortest ones which produce a unit cell with non-zero volume.

Type: boolean
Default: "false"
Use: optional
XPath: /input/structure/@primcell


Attribute: rmtapm

This attribute assigns the two parameters governing the automatic generation of the muffin-tin radii. When the attribute autormt is set to "true", the muffin-tin radii are determined according to the following expression

(3)
\begin{align} R_i\propto 1+\zeta|Z_i|^{1/3}, \end{align}

where $Z_i$ is the atomic number of the $i$ th species, $\zeta$ is stored in rmtapm(1). The distance between the muffin-tin speheres is determined by the value of rmtapm(2): When rmtapm(2)=1, the closest muffin-tin spheres will touch each other.

Type: vect2d
Default: "0.25d0 0.95d0"
Use: optional
XPath: /input/structure/@rmtapm


Attribute: speciespath

The path to the directory containing the species files. Alternatively, it can be defined as an HTTP URL, in this case the wget utility must be installed.

Type: anyURI
Use: required
XPath: /input/structure/@speciespath


Attribute: tshift

If "true", the crystal is shifted such that the atom closest to the origin is exactly at the origin.

Type: boolean
Default: "true"
Use: optional
XPath: /input/structure/@tshift


Attribute: vacuum

Determines the size of the vacuum around the molecule, see the molecule attribute.

Type: fortrandouble
Default: "10.0d0"
Use: optional
Unit: Bohr
XPath: /input/structure/@vacuum

Element: crystal

Defines the unit cell of the crystal via the 3 basis vectors.

contains: basevect (required)
XPath: /input/structure/crystal

This element allows for specification of the following attributes: scale, stretch

Attribute: scale

Scales all the lattice vectors by the same factor. This is useful for varying the volume.

Type: fortrandouble
Default: "1.0d0"
Use: optional
Unit: 1
XPath: /input/structure/crystal/@scale


Attribute: stretch

Allows for an individual scaling of each lattice vector separately. "1 1 1" means no scaling.

Type: vect3d
Default: "1.0d0 1.0d0 1.0d0 "
Use: optional
XPath: /input/structure/crystal/@stretch

Element: basevect

Defines one basis vector in Cartesian coordinates.

Type: vect3d
Unit: Bohr
XPath: /input/structure/crystal/basevect

Element: species

Defines the atomic species, i.e., the chemical element. Aatomic coordinates and, optionally, quantities relevant for magnetic calculations are defined in the subelement(s) atom.

contains: atom (required)
LDAplusU (optional)
XPath: /input/structure/species

This element allows for specification of the following attributes: speciesfile (required), rmt

Attribute: rmt

Defines the muffin-tin radius. This optional parameter allows to override the value either specified in the species file or generated by automatic determination. The muffin-tin radius defines the region around the atomic nucleus where the wave function is expanded in terms of atomic-like functions. In contrast, the interstitial region, i.e., the region not belonging to any muffin-tin sphere, is described by planewaves.

Type: fortrandouble
Default: "-1.0d0"
Use: optional
Unit: Bohr
XPath: /input/structure/species/@rmt


Attribute: speciesfile

Defines the file that contains the species definition. It is looked up in the species directory specified by speciespath. By default, the name of the file is element.xml, e.g., Ag.xml.

Type: anyURI
Use: required
XPath: /input/structure/species/@speciesfile

Element: atom

Defines the position and other attributes of one atom in the unit cell.

Type: no content
XPath: /input/structure/species/atom

This element allows for specification of the following attributes: coord (required), bfcmt, mommtfix

Attribute: bfcmt

Muffin-tin external magnetic field in Cartesian coordinates.

Type: vect3d
Default: "0.0d0 0.0d0 0.0d0"
Use: optional
XPath: /input/structure/species/atom/@bfcmt


Attribute: coord

Atom position in lattice coordinates.

Type: vect3d
Use: required
Unit: lattice coordinates
XPath: /input/structure/species/atom/@coord


Attribute: mommtfix

The desired muffin-tin moment for a Fixed Spin Moment (FSM) calculation.

Type: vect3d
Default: "0.0d0 0.0d0 0.0d0"
Use: optional
XPath: /input/structure/species/atom/@mommtfix

Element: LDAplusU

The LADplusU element is used to specify the J, U, and l parameters of an atomic species. To switch on the LDAplusU feature one needs to set the ldapu attribute of the groundstate element.

Type: no content
XPath: /input/structure/species/LDAplusU

This element allows for specification of the following attributes: J, U, l

Attribute: J

Type: fortrandouble
Default: "0.0d0"
Use: optional
XPath: /input/structure/species/LDAplusU/@J


Attribute: U

Type: fortrandouble
Default: "0.0d0"
Use: optional
XPath: /input/structure/species/LDAplusU/@U


Attribute: l

Type: integer
Default: "-1"
Use: optional
XPath: /input/structure/species/LDAplusU/@l

Reused Elements

The following elements can occur more than once in the input file. There for they are listed separately.

Data Types

The Input definition uses derived data types. These are described here.

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