Brief Introduction of the Input Files
The following files are the central input files for ABACUS. Before executing the program, please make sure these files are prepared and stored in the working directory. Here we give some simple descriptions XXX. For more details, users should consult the Advanced session.
INPUT file contains parameters that control the type of calculation as well as a variety of settings.
Below is an example
INPUT file with some of the most important parameters that need to be set:
INPUT_PARAMETERS suffix MgO ntype 2 pseudo_dir ./ orbital_dir ./ ecutwfc 100 # Rydberg scf_thr 1e-4 # Rydberg basis_type lcao calculation scf # this is the key parameter telling abacus to do a scf calculation
The parameter list always starts with key word
INPUT_PARAMETERS. Any content before
INPUT_PARAMETERS will be ignored.
Any line starting with
/ will also be ignored.
Each parameter value is provided by specifying the name of the input variable and then putting the value after the name, separated by one or more blank characters(space or tab). The following characters (≤ 150) in the same line will be neglected.
Depending on the input variable, the value may be an integer, a real number or a string. The parameters can be given in any order, but only one parameter should be given per line.
Furthermore, if a given parameter name appeared more than once in the input file, only the last value will be taken.
Note: if a parameter name is not recognized by the program, the program will stop with an error message.
In the above example, the meanings of the parameters are:
suffix: the name of the system, default
ntype: how many types of elements in the unit cell
pseudo_dir: the directory where pseudopotential files are provided
orbital_dir: the directory where orbital files are provided
ecutwfc: the plane-wave energy cutoff for the wave function expansion (UNIT: Rydberg)
scf_thr: the threshold for the convergence of charge density (UNIT: Rydberg)
basis_type: the type of basis set for expanding the electronic wave functions
calculation: the type of calculation to be performed by ABACUS
For a complete list of input parameters, please consult this instruction.
Note: Users cannot change the filename “INPUT” to other names.
The structure file contains structural information about the system, e.g., lattice constant, lattice vectors, and positions of the atoms within a unit cell. The positions can be given either in direct or Cartesian coordinates.
An example of the
STRU file is given as follows :
#This is the atom file containing all the information #about the lattice structure. ATOMIC_SPECIES Mg 24.305 Mg_ONCV_PBE-1.0.upf # element name, atomic mass, pseudopotential file O 15.999 O_ONCV_PBE-1.0.upf NUMERICAL_ORBITAL Mg_gga_8au_100Ry_4s2p1d.orb O_gga_8au_100Ry_2s2p1d.orb LATTICE_CONSTANT 1.8897259886 # 1.8897259886 Bohr = 1.0 Angstrom LATTICE_VECTORS 4.25648 0.00000 0.00000 0.00000 4.25648 0.00000 0.00000 0.00000 4.25648 ATOMIC_POSITIONS Direct #Cartesian(Unit is LATTICE_CONSTANT) Mg #Name of element 0.0 #Magnetic for this element. 4 #Number of atoms 0.0 0.0 0.0 0 0 0 #x,y,z, move_x, move_y, move_z 0.0 0.5 0.5 0 0 0 #x,y,z, move_x, move_y, move_z 0.5 0.0 0.5 0 0 0 #x,y,z, move_x, move_y, move_z 0.5 0.5 0.0 0 0 0 #x,y,z, move_x, move_y, move_z O #Name of element 0.0 #Magnetic for this element. 4 #Number of atoms 0.5 0.0 0.0 0 0 0 #x,y,z, move_x, move_y, move_z 0.5 0.5 0.5 0 0 0 #x,y,z, move_x, move_y, move_z 0.0 0.0 0.5 0 0 0 #x,y,z, move_x, move_y, move_z 0.0 0.5 0.0 0 0 0 #x,y,z, move_x, move_y, move_z
Note: users may choose a different name for their structure file using the keyword
stru_file. The order of the pseudopotential file list and the numerical orbital list (if LCAO is applied) MUST be consistent with that of the atomic type given in
For a more detailed description of STRU file, please consult here.
This file contains information of the kpoint grid setting for the Brillouin zone sampling.
An example of the
KPT file is given below:
K_POINTS 0 Gamma 4 4 4 0 0 0
Note: users may choose a different name for their k-point file using keyword
For a more detailed description, please consult here.
The pseudopotential files
Norm-conserving pseudopotentials are used in ABACUS, in the UPF file format.The filename of each element’s pseudopotential needs to be specified in the STRU file, together with the directory of the pseudopotential files unless they are already present in the working directory.
More information on pseudopotentials is given here.
The numerical orbital files
This part is only required in LCAO calculations. The filename for each element’s numerical orbital basis needs to be specified in the STRU file, together with the directory of the orbital files unless they are already present in the working directory. ABACUS provides numerical atomic basis sets of different accuracy levels for most elements commonly used. Users can download these basis sets from the website. Moreover, users can generate numerical atomic orbitals by themselves, and the procedure is provided in this short introduction.