ReSpect program

method

Specify the type of molecular Hamiltonian for SCF (and subsequent property) calculations.

Input block

Short variant

method: 
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                                     
[hamiltonian]
                                                     
                                                  
                                               
                                                  
                                               
                                                  
                                                
                                            
                                             
/
                                            
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                               
                                                  
                                                     
[functional]

Extended variant

method:

hfx: [integer]

functional: [functional]

hamiltonian: [hamiltonian]

Default

none

Example

method: hf

method: ks-1eX2C/b3lyp

method: 
   hamiltonian: ks-1eX2C
   functional:  b3lyp
   hfx:         40

Note

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

geometry

Specify the molecular geometry.

Input block

Extended variant

geometry:

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

Default

none

Example

#water in the xyz format
geometry:
   H  -0.756690  +0.466877  0.000000 
   H  +0.756690  +0.466877  0.000000 
   O  +0.000000  -0.119015  0.000000

#ethylene in the z-matrix format
geometry:
   H
   C  1  1.08
   H  2  1.08  1  120.0
   C  2  1.40  3  120.0  1  180.0
   H  4  1.08  2  120.0  1  180.0
   H  4  1.08  2  120.0  1  0.000

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".

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, the orbital basis "ucc-pvdz" 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 "eri" 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.

eri

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

Input block

Short variant

Extended variant

eri:

class: [string]

threshold: [real]

acceleration: [string]

Default

eri:
   class:        llll
   threshold:    1.e-10
   acceleration: none

Example

eri: ri-j

eri:
   class:        ssss/abcd 
   threshold:    1.e-15
   acceleration: ri-j

grid

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

Input block

Short variant

grid: 
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                                     
[grid-type]

Extended variant

grid:

[element-index]:  [grid-type]

[element-symbol]: [grid-type]

Default

grid: medium

Example

grid: large

grid:
     C: medium
     5: coarse

pcm

Specify the polarizable continuum solvent model for SCF (and subsequent property) calculations.

Input block

Extended variant

pcm:

area: [real]

solver: [solver]

solvent: [solvent]

probe-radius: [real]

radii-set: [radii-set]

Default

pcm:
   area:         0.3
   solver:       cpcm
   solvent:      none 
   radii-set:    allinger 
   probe-radius: 1.385

Example

initmo

Provide starting/initial molecular orbitals for SCF calculations.

Input line

Default

initmo: atomic

Example

initmo: eht

charge

Specify the total molecular charge.

Input line

Default

charge: 0

Example

charge: -2

multiplicity

Specify the spin multiplicity.

Input line

multiplicity:
                               
                                  
[integer]

Default

multiplicity: 1  #singlet

Example

multiplicity: 3  #triplet

convergence

Specify the convergence threshold for SCF iterations.

Input line

convergence:
                               
                                  
[real]

Default

convergence: 1.0e-06

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 SCF iterations.

Input line

maxiterations:
                               
                                  
[integer]

Default

maxiterations: 30

Example

maxiterations: 25

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 molecular 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 molecular 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 SCF iterations.

Input line

checkpoint:
                               
                                  
[integer]

Default

checkpoint: 10

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.

spin

Control the initial orientation of spin polarization in relativistic SCF calculations.

Input line

Default

spin: z

Example

spin: x

Note

This keyword plays an important role only in relativistic Kramers-unrestricted calculations of open-shell molecules, in particular in connections with the EPR property calculations, as it controls the initial orientation of the spin polarization. In non-relativistic regime, however, the keyword does not make a sense and is therefore ignored.

spinfix

Impose a spin fixation procedure in relativistic SCF calculations of open-shell molecules.

Input line

Default

spinfix: off

Example

spinfix: on

Note

This keyword plays an important role only in relativistic Kramers-unrestricted calculations of open-shell molecules, in particular in connections with the EPR property calculations, as it enforces the orientation of the spin polarization during SCF iterations. In non-relativistic regime, however, the keyword does not make a sense and is therefore ignored.

geo-units

Specify units in which the molecular geometry is provided.

Input line

geo-units:
                               
                                  
[string]

Default

geo-units: angstrom

Example

geo-units: bohr

mo-analysis

Specify the type of molecular orbitals analysis.

Input line

mo-analysis:
                               
                                  
[string]

Default

none

Example

mo-analysis: mulliken

Warning

So far, the keyword works only for the non-relativistic type of Hamiltonians.

[string]	description
eht	extended Hueckel's theory
bare	one-electron (bare nucleus) Hamiltonian
atomic	superposition of atomic densities

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

[string]	description
x	initial spin polarization along the x-coordinate
y	initial spin polarization along the y-coordinate
z	initial spin polarization along the z-coordinate

[string]	description
on	the initial orientation of the spin polarization will be preserved during SCF iterations
off	the initial orientation of the spin polarization will not be preserved during SCF iterations

[string]	description
angstrom
bohr

[string]	description
basic
mulliken

[hamiltonian]	description
hf	one-component Hartree–Fock Hamiltonian
ks	one-component Kohn–Sham Hamiltonian
hf-dkh2	one-component Hartree–Fock Hamiltonian with the scalar one-electron relativistic corrections due to Douglas–Kroll–Hess of second-order (DKH2)
ks-dkh2	one-component Kohn–Sham Hamiltonian with the scalar one-electron relativistic corrections due to Douglas–Kroll–Hess of second-order (DKH2)
hf-1eX2C	two-component Hartree–Fock Hamiltonian with the exact two-component (X2C) transformation of the one-electron Dirac Hamiltonian
ks-1eX2C	two-component Kohn–Sham Hamiltonian with the exact two-component (X2C) transformation of the one-electron Dirac Hamiltonian
mdhf	four-component Dirac–Hartree–Fock Hamiltonian
mdks	four-component Dirac–Kohn–Sham Hamiltonian

[functional]	description
slaterx	Slater local exchange DFT functional J. C. Slater, Phys. Rev. 81, 385–390 (1951)
svwn5	Slater local exchange and Vosko–Wilk–Nusair local correlation DFT functional (LDA-type) J. C. Slater, Phys. Rev. 81, 385–390 (1951) S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200–1211 (1980)
bp86	Becke non-local exchange and Perdew non-local correlation DFT functional (GGA-type) A. D. Becke, Phys. Rev. A 38, 3098–3100 (1988) J. P. Perdew, Phys. Rev. B 33, 8822–8824 (1986) Erratum, Phys. Rev. B 34, 7406–7406 (1986) J. C. Slater, Phys. Rev. 81, 385–390 (1951) S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200–1211 (1980)
pp86	Perdew–Wang non-local exchange and correlation DFT functional (GGA-type) J. P. Perdew, Phys. Rev. B 33, 8822–8824 (1986) Erratum, Phys. Rev. B 34, 7406–7406 (1986) J. P. Perdew, and Y. Wang, Phys. Rev. B 33, 8800–8802 (1986) Erratum, Phys. Rev. B 40, 3399–3399 (1989) J. C. Slater, Phys. Rev. 81, 385–390 (1951) S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200–1211 (1980)
kt2	Keal–Tozer non-local exchange and Vosko–Wilk–Nusair correlation DFT functional (GGA-type) T. W. Keal, and D. J. Tozer, J. Chem. Phys. 119, 3015 (2003) J. C. Slater, Phys. Rev. 81, 385–390 (1951) S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200–1211 (1980)
blyp	Becke non-local exchange and Lee–Yang–Parr correlation DFT functional (GGA-type) A. D. Becke, Phys. Rev. A 38, 3098–3100 (1988) C. Lee, W. Yang, and R. G. Parr, Phys. Rev. B 37, 785–789 (1988) J. C. Slater, Phys. Rev. 81, 385–390 (1951)
pbe	Perdew–Burke–Ernzerhof exchange and correlation DFT functional (GGA-type) J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865–3868 (1996) Erratum, Phys. Rev. Lett. 78, 1396–1396 (1997) J. C. Slater, Phys. Rev. 81, 385–390 (1951)
b3lyp	Becke three-parameters exchange and Lee–Yang–Parr correlation DFT functional (hybrid-type) A. D. Becke, Phys. Rev. A 38, 3098–3100 (1988) C. Lee, W. Yang, and R. G. Parr, Phys. Rev. B 37, 785–789 (1988) P. J. Stephens, F. J. Devlin, C. F. Chabalowski, and M. J. Frisch, J. Phys. Chem. 98, 11623–11627 (1994) J. C. Slater, Phys. Rev. 81, 385–390 (1951) S. H. Vosko, L. Wilk, and M. Nusair, Can. J. Phys. 58, 1200–1211 (1980)
pbe0	Perdew–Burke–Ernzerhof exchange and correlation DFT functional (hybrid-type) J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865–3868 (1996) Erratum, Phys. Rev. Lett. 78, 1396–1396 (1997) C. Adamo, and V. Barone, J. Chem. Phys. 110, 6158–6170 (1999) J. C. Slater, Phys. Rev. 81, 385–390 (1951)

[string]	description
llll	evaluate only the [LL\|LL] class (default for one- and two-component Hamiltonians)
ssll	evaluate exactly [LL\|LL], [LL\|SS] and [SS\|LL] classes but neglect [SS\|SS]
ssss/aabb	evaluate exactly [LL\|LL], [LL\|SS] and [SS\|LL] classes and use an one-center approximation for [SS\|SS]. In this approximation, both functions in [SS\| and \|SS] should share the same atomic center, otherwise they are excluded from evaluation. This is the default for four-component Hamiltonians.
ssss/abcd	evaluate exactly all four ERI classes

[string]	description
c4	complex algebra over 4Nx4N matrices
h2	quaternion algebra over 2Nx2N matrices

[string]	description
ri-j	resolution-of-identity (RI) for the two-electron Coulomb term
none	no approximation imposed

[eri]	description
ri-j	resolution-of-identity (RI) for the two-electron Coulomb term
exact	exact evaluation of four-center two-electron integrals

[string]	description
coarse
medium	default grid.
large

[solver]	description
iefpcm	collocation solver for a general dielectric medium
cpcm	collocation solver for a conductor-like approximation to the dielectric medium

[solvent]	description
water
dimethylsulfoxide
nitromethane
acetonitrile
methanol
ethanol
acetone
dichloroethane
methylenechloride
tetrahydrofurane
aniline
chlorobenzene
chloroform
toluene
dioxane
benzene
cyclohexane
n-heptane
explicit	set own static dielectric permittivity of the medium. The real value must >= 1.0.

[radii-set]	description
allinger	MM3 set of N.L. Allinger, X. Zhou, and J. Bergsma, J. Mol. Struct.: THEOCHEM, 312, 69 (1994). NOTE: all radii are scaled down by factor 1.2 compared to the original paper
uff	A. K. Rappe, C. J. Casewit, K. S. Colwell, W. A. Goddard, W. M. Skiff, J. Am. Chem. Soc., 114, 10024 (1992)
bondi	A. Bondi, J. Phys. Chem., 68, 441 (1964); M. Mantina, A. C. Chamberlin, R. Valero, C. J. Cramer, D. G. Truhlar, J. Phys. Chem. A, 113, 5806 (2009)

Latest Posts

Webpage update

February 15, 2024

Program update: ReSpect 5.1.0

February, 2019

Latest Publications

Relativistic attosecond time-resolved XAS in ReSpect (J.Phys.Chem.Lett)

February 9, 2023

Accurate XAS spectra with new (e)amfX2C Hamiltonians (J.Phys.Chem.A)

January 17, 2023

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Our Contacts

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