ReSpect program

mowindow

Enable the selective perturbation (SP) approach introduced in the context of RT-TDSCF in Kadek et al. PCCP 17, 22566 (2015) but applicable to CPP calculations as well. SP enables to represent the perturbation and response operators only in selected molecular orbitals, allowing thus to eliminate nonphysical excitations that are artifacts of the finite basis representation in core-level spectroscopies.

Input block

Extended variant

mowindow:

occupied: [intial-mo-index] - [final-mo-index]

virtual:  [intial-mo-index] - [final-mo-index]

Default

none

Example

mowindow:
         occupied:   4-6

mowindow:
         occupied:   7-10
         virtual:   15-46

Note

By default, the entire orbital spectrum is considered.

Occupied and virtual orbitals must be within their respective range. The range for occupied orbitals is from 1 to HOMO, whereas the range for virtual orbitals is from HOMO+1 to the total number of MOs.

Tip

SP turns out to be particularly useful for X-ray spectroscopies, where excitations occur only from specific core-shell orbitals. Here, we recommed to select for perturbation only the core-shell occupied MOs.

transition-analysis

Enable the transition density matrix analysis (TDMA) introduced in the context of RT-TDSCF in Repisky et al. JCTC 11, 980 (2015) but applicable to CPP calculations as well. TDMA enables to perform the orbital analysis of spectral transitions in RT-TDSCF simulations.

Input block

Extended variant

transition-analysis:

occupied: [intial-mo-index] - [final-mo-index]

virtual:  [intial-mo-index] - [final-mo-index]

threshold: [real]

Default

none

Example

transition-analysis:
         occupied:   8-10
         virtual:   11-25
         threshold: 1.0e-5

Note

By default, TDMA is disabled.

Occupied and virtual orbitals must be within their respective range. The range for occupied orbitals is from 1 to HOMO, whereas the range for virtual orbitals is from HOMO+1 to the total number of MOs.

Tip

Since TDMA may lead to an extensive data printout, we recommend to select only those orbitals relevant for the spectroscopy of interest.

xc

Specify details associated with the evaluation of the exchange–correlation (xc) kernel.

Input block

Short variant

xc: 
                                         
                                            
                                               
                                                
                                               
                                               
                                                  
                                                     
[functional]

Extended variant

xc:

functional: [functional]

noncollinearity: [string]

Default

xc:
  functional      : from-scf
  noncollinearity : v2019

Example

xc: XALDA

xc:
     functional      : XALDA
     noncollinearity : v2005

Warning

The use of ALDA or XALDA options is not recommended, because they usually approximate the full xc kernel. Their use is only recommended when comparing the calculated data to implementations in other quantum chemistry programs, where those approximations can not be avoided.

property

Specify the property of interest. (mandatory keyword)

Input line

Default

none

Example

property: eas

dipole-gauge

Specify the gauge for the interaction with external electromagnetic field.

Input line

dipole-gauge:
                               
                                  
[string]

Default

dipole-gauge: length (if property is pol/eas), velocity (if property is ord/ecd)

Example

dipole-gauge: length

solver

Specify the type of solver used to solve the (damped) linear response equation.

Input line

Default

solver: subspace

Example

solver: diis

maxiterations

Define the maximum number of micro-iterations for the solver.

Input line

maxiterations:
                               
                                  
[integer]

Default

maxiterations: 30

Example

maxiterations: 50

checkpoint

Define the frequency of data checkpointing during the iterations.

Input line

checkpoint:
                               
                                  
[integer]

Default

checkpoint: 5

Example

checkpoint: 10

convergence

Define the convergence threshold for the CPP solver.

Input line

convergence:
                               
                                  
[real]

Default

convergence: 0.0001

Example

convergence: 1.0e-5

Note

The quantity tested for convergence is the norm of the residue vector divided by the norm of the solution vector.

frequencies

Specify the (angular) frequencies at which to solve the (damped) linear reponse equation.

Input line

frequencies:
                               
                                  
[real1 integer x real2]

Default

frequencies: 0.0

Example

frequencies: 0.0 50x0.07

frequencies: 0.2 0.5 0.6 1.00

frequencies: 0.2 0.5 0.6

Note

The units for the frequencies are specified by the keyword units.

damping

Specify the damping parameter for the damped linear reponse equation.

Input line

Default

damping: 0.0

Example

damoing: 0.1

Note

The units for the damping parameter are specified by the keyword units.

units

Specify the units for the frequencies and the damping parameter in the (damped) linear reponse equation.

Input line

Default

units: au

Example

units: ev

Note

The units for the damping parameter are specified by the keyword units.

[string]	description
pol	frequency-dependent linear electric dipole polarizability (EAS spectrum is printed as well)
eas	electron absorption spectroscopy (EAS) (frequency-dependent polarizability is printed as well)
ord	optical rotatory dispersion (ORD) spectroscopy (ECD spectrum is printed as well)
ecd	electronic circular dichroism (ECD) spectroscopy (ORD spectrum is printed as well)

[string]	description
length	Length gauge, position operator used as perturbation.
velocity	Velocity gauge, momentum operator used as perturbation, valid only for ORD/ECD calculations.

[string]	description
subspace	Iterative subspace solver (Davidson-like method for linear system).
diis	DIIS solver (available for static polarizability only).

[string]	description
au	Hartree atomic units.
ev	Electronvolts.
cm-1	Wavenumber in reciprocal centimeters.
nm	Wavelength in nanometers.

[functional]	description
xalda	Uses SVWN5 functional for the exchange-correlation kernel, regardless of the type of the xc functional in the scf step. Full Hartree–Fock kernel is calculated with the percentage of the exchange admixture taken from the scf step.
alda	Uses SVWN5 functional for the exchange-correlation kernel, regardless of the type of the xc functional in the scf step. The Hartree–Fock exchange kernel is omitted even if the scf step was calculated using hybrid functional. Note that the Coulomb part of the Hartree–Fock kernel is not omitted. This is relevant for the open-shell calculation where Coulomb part is nonzero.
from-scf	Functional for calculation of the xc kernel matches the functional from the scf step.

[string]	description
v2019	The 2019 version of the noncollinear xc kernel for both open- and closed-shell systems have been published in the framework of LR-TDDFT [Komorovsky2019]. This is the most general formulation of the noncollinear scheme and can be used for prediction of all spectroscopic parameters available in the ReSpect. The xc potential and kernel is formulated in the analytic form. The closed-shell limit of the open-shell noncollinear scheme corresponds to the xc kernel for the first time presented in ref [Bast2009]. In the output files we refer to closed-shell formulation of the noncollinear xc scheme as WB2009 ([Wang2004] + [Bast2009]). The implementation details of the 2019 version of the noncollinear xc kernel is summarized in Table III in reference ReSpect article [Repisky2020] labeled as recommended option (superscript b). F. Wang and T. Ziegler, J. Chem. Phys. 121, 12191 (2004) R. Bast, H. J. A. Jensen, and T. Saue, Int. J. Quant. Chem. 109, 2091–2112 (2009) S. Komorovsky, P. Cherry, and M. Repisky, J. Chem. Phys. 151, 184111 (2019) M. Repisky, S. Komorovsky, M. Kadek, L. Konecny, U. Ekstrom, E. Malkin, M. Kaupp, K. Ruud, O. L. Malkina, and V. G. Malkin, J. Chem. Phys. 152, 184101 (2020)

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

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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