ReSpect program

method

Specify the type of electronic Hamiltonian for periodic SCF (pSCF) calculations.

Input block

Short variant

method: 
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                                     
[hamiltonian]
                                                     
                                                  
                                               
                                                  
                                                
                                            
                                             
/
                                            
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                               
                                                  
                                                     
[functional]

Extended variant

method:

functional: [functional]

hamiltonian: [hamiltonian]

Default

none

Example

method: mdks/pbe

method: 
   hamiltonian: mdks
   functional:  pbe

Note

The explicit definition of [functional] is mandatory for all [hamiltonian]s of the Kohn–Sham type.

geometry

Specify the coordinates and types of atoms in the reference unit cell.

Input block

Extended variant

geometry:

[element-symbol] [x] [y] [z]

Default

none

Example

geometry:
   H  -0.756690  +0.466877  0.000000 
   H  +0.756690  +0.466877  0.000000 
   O  +0.000000  -0.119015  0.000000

Note

Angstroms are used as default units for geometry.

The geometry can be provided either in the Cartesian (xyz) format or in the Z-matrix format.

Tip

The default units can be changed by the keyword "geo-units".

lattice

Specify the primitive Bravais lattice vectors for 1D, 2D, or 3D systems.

Input block

Extended variant

lattice:

#1D systems
a1: [x]

#2D systems
a1: [x] [y]
a2: [x] [y]

#3D systems
a1: [x] [y] [z]
a2: [x] [y] [z]
a3: [x] [y] [z]

Default

none

Example

#1D
lattice:
    a1:  1.5

#2D
lattice:
    a1:  1.0  0.0
    a2:  0.0  1.2

#3D
lattice:                                
    a1:  1.0  0.0  0.0
    a2:  0.0  1.1  0.0
    a3:  0.0  0.0  1.2

Note

Angstroms are used as default units for lattice.

Tip

The default units can be changed by the keyword "geo-units".

basis

Specify atomic orbital basis sets.

Input block

Short variant

basis: 
                                         
                                            
[basis-name]

Extended variant

basis:

all             : [basis-name]

[element-index] : [basis-name]

[element-symbol]: [basis-name]

Default

none

Example

In this example, orbital ucc-pvdz basis is assigned to all elements.

basis: ucc-pvdz

In this example, the orbital basis "upc-1" is assigned first to all elements. Then, the basis is replaced by "ucc-pvdz" for the 4th element (as specified in the input block "geometry") and "dyall-vdz" for all bromine atoms.

basis:
   all : upc-1 
   4   : ucc-pvdz
   Br  : dyall-vdz

Note

In relativistic calculations the orbital basis must be in an uncontracted form. All basis sets from the internal program library are of this form.

Tip

The complete list of available [basis-name]s can be found here.

auxbas

Specify atomic auxiliary basis sets.

Input block

Short variant

auxbas: 
                                         
                                            
[basis-name]

Extended variant

auxbas:

all             : [basis-name]

[element-index] : [basis-name]

[element-symbol]: [basis-name]

Default

none

Example

In this example, the auxiliary basis "ucc-pvtz" is assigned to all elements.

auxbas: ucc-pvtz

In this example, the auxiliary basis "upc-1" is assigned first to all elements. Then, the basis is replaced by "ucc-pvdz" for the 4th element (as specified in the input block "geometry") and "dyall-vdz" for all bromine atoms.

auxbas:
   all : upc-1 
   4   : ucc-pvdz
   Br  : dyall-vdz

Note

The use of auxiliary basis makes sense only in connection with an approximative evaluation of electron repulsion integrals (ERI) by means of the resolution-of-identity (RI) technique. This is controled by the keyword "acceleration" in the "peri" block.

The names of matching orbital and auxiliary basis sets are identical. Therefore, one can omit the definition of auxiliary basis, provided the orbital basis was selected from the internal program library. In this case, the program will assign the auxiliary basis automatically.

peri

Specify details associated with the evaluation of periodic electron repulsion integrals (PERI) and related two-electron Fock contributions.

Input block

Short variant

Extended variant

peri:

threshold: [real]

thr-relevant-omega: [real]

thr-gauss-extent: [real]

well-separated: [int]

lmax: [int]

box-length: [real]

acceleration: [string]

Default

peri:
   threshold:    1.e-11
   thr-relevant-omega:  1.e-12
   thr-gauss-extent:  1.e-9
   well-separated:  2 (RI-J), 3 (CFMM)
   lmax: 20
   box-length: 2.0
   acceleration: none

Example

peri: ri-j

peri:
   threshold:    1.e-10
   well-separated:  5
   lmax: 15
   box-length: 4.0
   acceleration: cfmm

grid

Specify atomic grids for the numerical evaluation of exchange-correlation DFT contributions.

Input block

Short variant

Extended variant

grid:

all: [string]

[element-symbol]: [string]

[element-index]: [string]

...

Default

grid: solids

Example

grid: large

grid:
     C: solids
     7: large

Note

It is strongly recommended to use "solids" option for all atoms, since it does not use adaptive grids for either angular or radial parts.

There can be multiple instances of [element-symbol] and [element-index] in the grid block.

While lines in the grid block can be mixed, they are always processed in the following order: "all", "element-symbol", and "element-index" keywords.

The order of processing the data matters, since the latter lines rewrite the data of the former lines. This way one can easily set the same grid for all carbons except the carbon number 7 (see example).

kmesh

Define the momentum-space grid by specifying the number of k points in each dimension.

Input line

kmesh:
                               
                                  
[int]x[int]x[int]

Default

kmesh: 1x1x1

Example

kmesh:  11x11x7

Note

The k-point grid is always centered on the gamma point.

Tip

For studies of 2D systems, it is sufficient to have only 1 k point in the non-periodic dimension, e.g. one can choose a grid of 15x15x1.

Warning

All three integers must be positive odd numbers.

initmo

Provide starting/initial crystalline orbitals for pSCF calculations.

Input line

Default

initmo: atomic

Example

initmo: atomic

Warning

bare nucleus guess should never be used for solids as it does not compensate the infinite positive charge with electron density.

convergence

Specify the convergence threshold for pSCF iterations.

Input line

convergence:
                               
                                  
[real]

Default

convergence: 1.0e-05

Example

convergence: 2.5e-5

Tip

We recommend to set the threshold value to ~1.0e-4 in cases when a loose SCF convergence is sufficient, such as in initial guess calculations, etc. For productive runs, however, the thresholds setup within the range 1.0e-5—1.0e-6 is advised. Tight convergence in the SCF is considered for thresholds below 1.0e-7.

maxiterations

Specify the maximum number of pSCF iterations.

Input line

maxiterations:
                               
                                  
[integer]

Default

maxiterations: 30

Example

maxiterations: 25

thr-basis-proj

Specify the threshold for projecting out redundant basis functions in the orthonormal basis used in the SCF calculations.

Input line

thr-basis-proj:
                               
                                  
[real]

Default

thr-basis-proj: 1.0e-07

Example

thr-basis-proj: 1.0e-8

Note

The SCF algorithm uses Lowdin Canonical Orthonormalization which allows for identifying and removing basis functions (in the orthonormal basis) that are redundant and cause issues with overcompleteness (linear dependences)

Warning

Too small (or zero) threshold causes numerical instabilities in some systems where standard GTO basis sets are overcomplete when used for solids.

Setting the threshold too large in the relativistic 4C calculations can cause breaking of the RKB condition.

nc-model

Specify the nuclear charge distribution model.

Input line

Default

nc-model: point

Example

nc-model: gauss

Note

Since the relativistic wave function exhibits a singularity at nuclear centers, users are advised to use a finite-size nuclear charge model such as "gauss" model.

cscale

Scale the speed of light by a factor.

Input line

Default

cscale: 1.0

Example

cscale: 20.0

Note

The scaling factor should be a positive real number. By setting cscale < 1.0, the speed of light decreases and periodic systems turn into a hyper-relativistic regime where all relativistic terms become amplified. On the other hand, by setting cscale > 1.0 the speed of light increases and periodic systems approach their non-relativistic limit.

Warning

Due to numerical reasons, the users are advised to set the cscale parameter within the limits: 0.1 < cscale < 50.0.

soscale

Scale the spin-orbit operators by a factor.

Input line

Default

soscale: 1.0

Example

soscale: 0.0

Note

The scaling factor should be a positive real number. By setting soscale = 0.0, one can switch off the spin-orbit interaction completely.

Warning

Due to numerical reasons, the users are advised to set the soscale parameter within the limits: 0.0 <= soscale <= 1.0.

checkpoint

Specify the frequency of data checkpointing during pSCF iterations.

Input line

checkpoint:
                               
                                  
[integer]

Default

checkpoint: 5

Example

checkpoint: 2

Tip

The importance of more frequent checkpointing -- storing intermediate SCF data to disk for the later reuse as a restart -- increases with the system size.

run-atoms

Specify if atomic SCF calculation to get atomic orbitals should preceed the periodic calculation.

Input line

run-atoms:
                               
                                  
[string]

Default

run-atoms: off

Example

run-atoms: on

geo-units

Specify units in which the molecular and lattice geometry are provided.

Input line

geo-units:
                               
                                  
[string]

Default

geo-units: angstrom

Example

geo-units: bohr

output

Control the amount of output information printed.

Input line

Default

output: standard

Example

output: long

metal-bands

Specify the number of bands that are not automatically assumed to be fully occupied (or unoccupied).

Input line

metal-bands:
                               
                                  
[integer]

Default

metal-bands: 10

Example

metal-bands: 0

Note

This only affects the disk/memory access and storage that are needed when the occupancy of bands is not known for all k points.

For instance, for many core orbitals, we can assume full (double) occupation for all k points - the SCF solver can handle such cases on-the-fly without accessing the disk.

The number set here should not affect majority of calculations, for gapped systems it is possible to set it to 0 to avoid disk access and memory usage altogether.

memory

Specify the available RAM memory (in GB) for each computational node that is used for storing k-space matrices.

Input line

Default

memory: 32

Example

memory: 64

Note

If the memory required for storing k-space matrices exceeds this number, the matrices will be stored to disk instead.

[string]	description
bare	one-electron (bare nucleus) Hamiltonian
atomic	superposition of atomic densities
scfun	superposition of molecular densities obtained from a converged nonperiodic SCF run

[string]	description
point	point nuclear charge distribution model
gauss	gaussian nuclear charge distribution model

[string]	description
off
on

[string]	description
angstrom
bohr

[string]	description
off	output completely suppressed
minimal	only very brief info printed
standard	basic amount of printed info
long	print also large matrices

[hamiltonian]	description
ks	one-component Kohn–Sham Hamiltonian
mdks	four-component Dirac–Kohn–Sham Hamiltonian

[functional]	description
slaterx	Slater exchange DFT functional
svwn5	Slater exchange and Vosko–Wilk–Nusair correlation DFT functional
bp86	Becke exchange and Perdew correlation DFT functional
pw91	Perdew–Wang exchange and correlation DFT functional
kt2	Keal–Tozer exchange and Vosko–Wilk–Nusair correlation DFT functional
blyp	Becke exchange and Lee–Yang–Parr correlation DFT functional
pbe	Perdew–Burke–Ernzerhof exchange and correlation DFT functional (GGA-type)

[string]	description
ri-j	resolution-of-identity (RI) for the two-electron Coulomb term
cfmm	continuous fast-multipole approach for the Coulomb interactions
none	no approximation imposed

[peri]	description
ri-j	resolution-of-identity (RI) for the two-electron Coulomb term
cfmm	continuous fast-multipole approach for the Coulomb interactions
exact	exact evaluation of four-center two-electron integrals

[string]	description
coarse	Adaptive angular part with a fixed radial number of points calculated as 30 + (10*p), where p is the period number of the defined element.
medium	Adaptive angular part with a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.
large	Adaptive angular part with a fixed radial number of points calculated as 50 + (10*p), where p is the period number of the defined element.
adaptive	Adaptive grid in both the radial and angular part calculated from the input basis.
solids	Angular part with 302 points and a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.

[string]	description
coarse	Adaptive angular part with a fixed radial number of points calculated as 30 + (10*p), where p is the period number of the defined element.
medium	Adaptive angular part with a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.
large	Adaptive angular part with a fixed radial number of points calculated as 50 + (10*p), where p is the period number of the defined element.
adaptive	Adaptive grid in both the radial and angular part calculated from the input basis.
solids	Angular part with 302 points and a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.

[string]	description
coarse	Adaptive angular part with a fixed radial number of points calculated as 30 + (10*p), where p is the period number of the defined element.
medium	Adaptive angular part with a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.
large	Adaptive angular part with a fixed radial number of points calculated as 50 + (10*p), where p is the period number of the defined element.
adaptive	Adaptive grid in both the radial and angular part calculated from the input basis.
solids	Angular part with 302 points and a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.

[string]	description
coarse	Adaptive angular part with a fixed radial number of points calculated as 30 + (10*p), where p is the period number of the defined element.
medium	Adaptive angular part with a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.
large	Adaptive angular part with a fixed radial number of points calculated as 50 + (10*p), where p is the period number of the defined element.
adaptive	Adaptive grid in both the radial and angular part calculated from the input basis.
solids	Angular part with 302 points and a fixed radial number of points calculated as 40 + (10*p), where p is the period number of the defined element.

Latest Posts

Webpage update

July 17, 2024

Program update: ReSpect 5.3.0

July, 2024

Latest Publications

Book chapter on relativistic real-time electron dynamics

May, 2024

Book chapter on relativistic theory of EPR and (p)NMR

May, 2024

Useful Links

Our Contacts

Hylleraas Centre
Department of Chemistry
UiT The Arctic University of Norway
Tromsø, NO-9037 Norway
Email: info@respectprogram.eu