SCTB: Input Files

Standard Input

All of the codes get their configuration information from standard input. The format for all of the eval_energy.*, eval_forces.*, and eval_virial.* programs is:

    N_CONFIGS
    <geometry of config 1>
    <geometry of config 2>
    .
    .
    .
    <geometry of config (N_CONFIGS)>

    N_ATOMS
    a_1_x a_1_y a_1_z
    a_2_x a_2_y a_2_z
    a_3_x a_3_y a_3_z
    p_1_x p_1_y p_1_z atomic_num_1
    p_2_x p_2_y p_2_z atomic_num_2
    .
    .
    .
    p_(N_ATOMS)_x p_(N_ATOMS)_y p_(N_ATOMS)_z atomic_num_(N_ATOMS)

• N_ATOMS: number of atoms
• a_i_[xyz]: [xyz] part of i'th supercell vector
• p_i_[xyz]: [xyz] position of atom i
• atomic_num_i: atomic number of atom i

All supercell and position vectors must be specified in units that are compatible with the TB model. All of the NRL-TB models assume input is in Angstroms.

Parameter File

Charge-Self-Consistency Parameter File (optional)

The tightbind.parms.self_cons file is the parameter file governing charge-self-consistency for the sctb package. If present, charge self-consistency is used. Its format is:

    do_interatomic
    N_types
    atomic_num_1 U_1
    atomic_num_2 U_2
    .
    .
    .
    atomic_num_N_types U_N_types

• do_interatomic: T for including interatomic charge interactions, F for just on-site U
• N_types: number of atomic types with U defined
• atomic_num_i U_i : atomic number of type, U of same type

Misc. Control Parameters File

The tb.data file contains misc. information needed to do the tight-binding calculation. Its format is:

1.0D-2
3 3 1
0
    

• The first line specifies the temperature used in the electronic Fermi distribution, in eV.
• The second line specifies how many periodic images to use along each lattice vector when searching for neighbors.
• The third line specifies the debugging level, 0 in this case.

k-point File (required by some)

The k-point mesh file k_pt_mesh.data is required by the *.nrl_tb_k_sum.* programs, but not used by the *.nrl_tb.*. Its format is:

    n_k
    k_1_1 k_1_2 k_1_3 k_1_weight
    k_2_1 k_2_2 k_2_3 k_2_weight
    .
    .
    .
    k_(n_k)_1 k_(n_k)_2 k_(n_k)_3 k_(n_k)_weight

• n_k: number of k-points
• k_i_[123]: position of k-pt # i in reciprocal lattice coordinates
• k_i_weight: weight of k-pt # i

Inversion symmetry in the BZ can always be used.

Interaction Targets File (optional)

The targets.data file specifies whether some atoms are restricted in their interactions, so only interactions with particular other atoms are included, or some interactions are excluded. If the file isn't present, all atoms interact with all other atoms (up to the relevant cutoff distances). The format is:

    n_targets
    target_atom_1 target_value_1
    target_atom_2 target_value_2
    .
    .
    .
    target_atom_(n_targets) target_value_(n_targets)

• n_targets: number of targetted atoms
• target_atom_i: number of atom being targetted
• target_value_i: value of target
  • if > 0, atom # target_atom_i only interacts with atom # target_value_i
  • if < 0, atom # target_atom_i doesn't interacts with atom # -target_value_i
  • if = 0, atom # target_atom_i doesn't interacts with anything