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| description | authors |
|---|---|
| How to build an input file for a ground state calculation | FJ |
This page gives hints on how to build an input file for a ground state calculation with the ABINIT package.
Introduction
The computation of the ground state energy of an assembly of nuclei and electrons placed in a repeated cell can be done using (1) plane waves and norm-conserving pseudopotentials, or, (2) so-called "Projector-Augmented Waves" (PAW method), with appropriate pseudoatomic data, or (3) wavelets. The wavelet framework is described topic:Wavelets.
In the plane wave framework, the program admits many different types of pseudopotentials. There are several complete sets of norm-conserving pseudopotentials available for most elements of the periodic table.
The recommended tables (GGA-PBE, GGA-PBEsol and LDA) come from the |pseudodojo| project with ONCVPSP pseudopotentials (cite:Hamann2013) both in scalar-relativistic format and fully-relativistic version with spin-orbit coupling. For PAW calculation,the recommended one (GGA-PBE and LDA) is the JTH table in the PAW XML format (cite:Jollet2014).
The choice between norm-conserving pseudopotentials or PAW is deduced automatically by the choice of the pseudopotential in the "files" file. An input file must specify the following items:
- the topic:crystal
- the set of topic:k-points used
- the topic:xc
- the convergence settings
- possibly topic:PAW special settings
- possibly, input variables for topic:spinpolarisation calculations.
An example of a minimal input file to calculate the ground state of crystalline aluminium is given here:
# Crystalline aluminum. Calculation of the total energy
# at fixed number of k points and broadening.
#Definition of occupation numbers
occopt 4
tsmear 0.05
#Definition of the unit cell
acell 3*7.60 # This is equivalent to 7.60 7.60 7.60
rprim 0.0 0.5 0.5 # FCC primitive vectors (to be scaled by acell)
0.5 0.0 0.5
0.5 0.5 0.0
#Definition of the atom types
ntypat 1 # There is only one type of atom
znucl 13 # The keyword "znucl" refers to the atomic number of the
# possible type(s) of atom. The pseudopotential(s)
# mentioned in the "files" file must correspond
# to the type(s) of atom. Here, the only type is Aluminum
#Definition of the atoms
natom 1 # There is only one atom per cell
typat 1 # This atom is of type 1, that is, Aluminum
xred 0.0 0.0 0.0 # This keyword indicate that the location of the atoms
# will follow, one triplet of number for each atom
# Triplet giving the REDUCED coordinate of atom 1.
#Definition of the planewave basis set
ecut 6.0 # Maximal kinetic energy cut-off, in Hartree
pawecutdg 10.0 #Maximal kinetic energy cut-off, in Hartree for the fine grid in case of PAW calculation
#Definition of the k-point grid
ngkpt 2 2 2 # This is a 2x2x2 FCC grid, based on the primitive vectors
chksymbreak 0
#Definition of the SCF procedure
nstep 10 # Maximal number of SCF cycles
toldfe 1.0d-6 # Will stop when, twice in a row, the difference
# between two consecutive evaluations of total energy
# differ by less than toldfe (in Hartree)
# This value is way too large for most realistic studies of materials
Related Input Variables
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Selected Input Files
{{ selected_input_files }}
Tutorials
- tutorial:base1 deals with the H2 molecule: get the total energy, the electronic energies, the charge density, the bond length, the atomisation energy
- tutorial:base2 deals again with the H2 molecule: convergence studies, LDA versus GGA
- tutorial:base3 deals with crystalline silicon (an insulator): the definition of a k-point grid, the smearing of the cut-off energy, the computation of a band structure, and again, convergence studies ...
- tutorial:base4] deals with crystalline aluminum (a metal), and its surface: occupation numbers, smearing the Fermi-Dirac distribution, the surface energy, and again, convergence studies ...