5. Input parameters in input.in

Input parameters that should be specified in input.in are listed below in the following format:

Keyword	TYPE
Default value	Available values
Detailed description

All inputs are case-sensitive. Keywords listed in the alphabetical order:

[Mandatory keywords] calc_method , calc_mode , pseudo_dir , qe_save_dir

[Optional keywords] A_dn_dn , A_up_dn , A_up_up , charge_tolerance , energy_tolerance , force_tolerance , includes_div_correction , is_heg , max_num_blocks_david , max_num_ionic_steps , max_num_iterations , mixes_density_matrix , mixing_beta , num_bands_tc , num_refresh_david , reads_crystal_structure , restarts , smearing_mode , smearing_width

5.1. Mandatory Keywords

calc_method	STRING
Mandatory (no default value)	FREE, HF, TC, BITC
Calculation method: free-electron mode (FREE), Hartree-Fock (HF), transcorrelated (TC), bi-orthogonal transcorrelated (BITC) methods. No electron-electron interaction is considered for FREE, i.e., the kinetic energy and pseudopotentials are only considered.

calc_mode	STRING
Mandatory (no default value)	SCF, BAND
Calculation mode. BAND calculation should be performed after SCF calculation.

pseudo_dir	STRING
Mandatory (no default value)	any
A directory where pseudopotential files are placed, e.g., /home/user/where_pseudopot_are_placed

qe_save_dir	STRING
Mandatory (no default value)	any
A save directory created by QE, e.g., /home/user/where_QEcalc_was_performed/prefix.save

5.2. Optional keywords

A_dn_dn	REAL
Default: 1.0	any
\(A_{\downarrow,\downarrow}\) in the RPA-type Jastrow function, \(\frac{A_{\sigma, \sigma'}}{|{\bf r}-{\bf r'}|}(1-e^{-|{\bf r}-{\bf r'}|/C_{\sigma,\sigma'}})\), normalized by \(A_0 = 1/\sqrt{4 \pi n}\), the value for the homogeneous electron gas having the same electron density \(n\) of the system. For example, A_dn_dn = 0.8 means \(A_{\downarrow,\downarrow}=0.8A_0\). \(C_{\downarrow,\downarrow}\) is determined so as to satisfy the cusp condition. Not used for calc_method = FREE or HF.

A_up_dn	REAL
Default: 1.0	any
\(A_{\uparrow,\downarrow}\), same as A_dn_dn. \(A_{\uparrow,\downarrow}=A_{\downarrow,\uparrow}\) is assumed.

A_up_up	REAL
Default: 1.0	any
\(A_{\uparrow,\uparrow}\), same as A_dn_dn. Users cannot specify different values for A_up_up and A_dn_dn in non-spin-polarized calculation.

charge_tolerance	REAL
Default: 1e-5 (1e-4 for ver.1.2 and before)	\(\geq 0\)
In \(e^-\). Convergence criteria for the charge density, used only for calc_mode = SCF.

energy_tolerance	REAL
Default: 1e-6 (1e-5 for ver.1.2 and before)	\(\geq 0\)
In Ht. Convergence criteria for the total energy (calc_mode = SCF) or a sum of eigenvalues (BAND).

force_tolerance (from ver.1.3)	REAL
Default: 1e-2	\(\geq 0\)
In eV/ang. Convergence criteria for the force in structural optimization (see max_num_ionic_steps)

includes_div_correction	BOOLEAN
Default: true	true, false
Whether the divergence correction in the reciprocal space is included. See our paper: M. Ochi, Comput. Phys. Commun. 287, 108687 (2023) . [arXiv]

is_heg	BOOLEAN
Default: false	true, false
Switches on the homogeneous-electron-gas mode where pseudopotentials and the Ewald energy are ignored. (i.e., energy contribution from a lattice is ignored.)

max_num_blocks_david	INTEGER
Default: 2	\(\geq 2\)
This keywords determines a size of subspace dimension for diagonalization. subspace dimension = max_num_blocks_david \(\times\) num_bands_tc. Increasing this value can improve convergence while computational time is proportional to it.

max_num_iterations	INTEGER
Default: 30 for calc_mode = SCF, 15 for calc_mode = BAND	\(\geq 0\)
Maximum number of iterations for the self-consistent-field loop (Also needed for calc_mode = BAND).

max_num_ionic_steps (from ver.1.3)	INTEGER
Default: 0	\(\geq 0\)
Maximum number of structural-optimization steps. Structural optimization is switched on when calc_mode = SCF and is_heg = false and max_num_ionic_steps > 0 and calc_method = HF or BITC.

mixes_density_matrix	BOOLEAN
Default: false	true, false
The density matrix (true) or the density (false) is used for mixing. The former with a small mixing_beta can improve the convergence of calculation while computational time will be longer (by about a factor of two). Used only for calc_mode = SCF. From ver.1.1.

mixing_beta	REAL
Default: 0.7	\(> 0\)
Mixing ratio for linear mixing: new density (or density matrix) = mixing_beta \(\times\) new density \(+\) \((1-\) mixing_beta \()\times\) old density. Used only for calc_mode = SCF.

num_bands_tc	INTEGER
Default: nbnd in QE	\(1 \leq\) num_bands_tc \(\leq\) nbnd in QE
The number of bands for calculating eigenvalues. Also see max_num_blocks_david.

num_refresh_david	INTEGER
Default: 1	\(\geq 1\)
Trial vectors are updated by num_refresh_david times for each update of the Fock operator.

reads_crystal_structure (from ver.1.3)	BOOLEAN
Default: false	true, false
When reads_crystal_structure = true, TC++ reads tc_crystal_structure.dat, which is dumped in a previous structural-optimization run. Note that this option is available only for the structural optimization (i.e. max_num_ionic_steps >0). Please also see How to use describing tc_crystsal_structure.dat.

restarts	BOOLEAN
Default: false	true, false
When restarts = true, TC++ restarts calculation from a previous run.

smearing_mode	STRING
Default: gaussian	fixed, gaussian
fixed: fixed occupation for each k-point, gaussian: Gaussian smearing with smearing_width. Recommended values are fixed for insulators and gaussian for metals.

smearing_width	REAL
Default: 0.01	\(\geq 0\) (A negative value will be ignored.)
In Ht. Not used for smearing_mode = fixed.

5.3. Examples of input.in

Example 1 (Minimum input.in for insulators)

calc_method    TC
calc_mode      SCF
pseudo_dir     /home/user/pseudopot
qe_save_dir    /home/user/QE/Si/prefix.save
smearing_mode  fixed

Example 2 (Minimum input.in for metals)

calc_method     TC
calc_mode       SCF
pseudo_dir      /home/user/pseudopot
qe_save_dir     /home/user/QE/Al/prefix.save
smearing_mode   gaussian
smearing_width  0.01

Example 3 (Restart calculation after Example 1)

calc_method     TC
calc_mode       SCF
pseudo_dir      /home/user/pseudopot
qe_save_dir     /home/user/QE/Si/prefix.save
smearing_mode   fixed
restarts        true

Example 4

calc_method     BITC
calc_mode       SCF
pseudo_dir      /home/user/pseudopot
qe_save_dir     /home/user/QE/something/prefix.save
smearing_mode   fixed
A_up_up         0.2
A_up_dn         0.2
A_dn_dn         0.2
max_num_iterations    15
max_num_blocks_david  5
mixes_density_matrix  true
mixing_beta     0.2

Example 5 (Structural optimization)

calc_method     BITC
calc_mode       SCF
pseudo_dir      /home/user/pseudopot
qe_save_dir     /home/user/QE/something/prefix.save
smearing_mode   fixed
max_num_iterations    20
max_num_ionic_steps   10

Example 6 (Restarted structural optimization reading tc_crystal_structure.dat)

calc_method     BITC
calc_mode       SCF
pseudo_dir      /home/user/pseudopot
qe_save_dir     /home/user/QE/something/prefix.save
smearing_mode   fixed
max_num_iterations       20
max_num_ionic_steps      10
reads_crystal_structure  true