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.

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.

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.

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

with

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.

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.

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

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.

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.

Attribute: tshift

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

Attribute: vacuum

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

Element: crystal

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

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.

Attribute: stretch

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

Element: basevect

Defines one basis vector in Cartesian coordinates.

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.

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.

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.

Element: atom

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

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

Attribute: bfcmt

Muffin-tin external magnetic field in Cartesian coordinates.

Attribute: coord

Atom position in lattice coordinates.

Attribute: mommtfix

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

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.

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

Attribute: J

Attribute: U

Attribute: 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.