Input

General structure

openLOWDIN input file consists on a plain text file with extension .lowdin which will be internally processed by a bash script to generate a Fortran namelist, creating the true input file for the code. The input file consists of different blocks enclosed by the lines BLOCK and END BLOCK, where “BLOCK” is one of the following sections:

  • GEOMETRY: define the position of the basis set centers, position of point charges, number and properties of quantum species.

  • TASKS : select the type of calculation to be performed by the code.

  • CONTROL: contains all general input parameters to control the behavior of the program, such as thresholds, maximum number of SCF cycles. See CONTROL for a full of keywords.

  • OUTPUT: request the calculation of other molecular property to visualize the molecular wave function or density. See Outputs

  • BASIS : declare a user defined basis. This can be alternatively defined in an external file. See Basis

  • INTERPOTENTIAL define an internal potential between pairs of quantum species. See Potentials

  • EXTERPOTENTIAL define an external potential for a quantum species. See Potentials

  • POTENTIAL declare a user defined potential built on gaussian type orbitals. See Potential Basis

  • INPUT_CI define the active space for each quantum species for CI calculations. See Configuration Interaction, CI

GEOMETRY block

The GEOMETRY block provides the information needed to build the molecular system as:

GEOMETRY
SPECIES_SYMBOL    BASIS_NAME  X_COORD Y_COORD Z_COORD
END GEOMETRY.

each line define either a new particle (quantum or point charge), or a new basis center (quantum particles only).

  • SPECIES_SYMBOL [character] symbol of the quantum particle as defined in the lib/dataBases/elementalParticles.lib and lib/dataBases/constantsOfCoupling.lib files, or the symbol of point charges defined in lib/dataBases/atomicElements.lib. See DataBases to define or redefine particles.

  • BASIS_NAME [character] for quantum particles, this corresponds to the name of the basis set, the code will look in the BASIS block or in the folder lib/basis. For point charge simply use dirac`

  • X_COORD, Y_COORD, Z_COORD [real] coordinates of the basis set center origin or position of the point charge.

Besides the above mandatory elements, the following flags can be added to modify the properties of the particles declared within the same line.

  • addParticles= [integer] modify the number of particles of a quantum species. Positive values increase number of particles, negative values decrease the number of particles. To not be confused with total charge. Default 0

  • multiplicity= [integer] declare the multiplicity of the quantum species as \(2S+1\), where \(S\) is the total spin within the quantum species. Default 1

  • q= [real] charge of the particle, quantum or point charge. Default defined in lib/dataBases/elementalParticles.lib

  • m= [real] mass of the particle, quantum only. Default defined in lib/dataBases/elementalParticles.lib

  • omega= [real] frequency of the harmonic potential of the particle, quantum only. Default 0.0 See Potentials

  • qdoCenterOf= [character] declare this particle as the point charge center of the quantum species in [character] within the QDO formalism. Default "NONE" See Quantum Drude Oscillators, QDOs

Note that a duplicate of one of the above keywords will overwrite the previous values for particles defined with the same name.

TASKS block

This block control the method to be computed

  • method= [character] Type of Hartree-Fock method See Hartree-Fock, HF

    "RHF"

    Restricted Hartree-Fock

    "UHF"

    Unrestricted Hartree-Fock

    "NONE"

    No Hartree-Fock. Default

  • optimizeGeometry= [logical] Activates geometry optimization. Default False

  • mollerPlessetCorrection= [integer] Order of Möller-Plesset Perturbation correction. Values: 2. Default 0 See Many-Body Perturbation Theory, MBPT

  • epsteinNesbetCorrection= [integer] Order of Epstein-Nesbet correction. Values: 2, 3. Default 0 See Many-Body Perturbation Theory, MBPT

  • propagatorTheoryCorrection= [integer] Order of propagator theory correction. Values: 2, 3. Default 0 See Propagathor Theory, PT

  • nonOrthogonalConfigurationInteraction= [logical] Performs non-Orthogonal Configuration Interaction calculation. Default False See Non-Orthogonal Configuration Interaction, NOCI

  • configurationInteractionLevel= [character] Select Configuration Interaction level. See Configuration Interaction, CI

    "CIS"

    Singles

    "CISD"

    Singles and doubles

    "CISD-"

    Singles, doubles interspecies only

    "CISD+"

    Singles, doubles, triples interpecies only

    "CISDT"

    Singles, doubles, triples

    "CISDTQ"

    Singles, doubles, triples, quadruples

    "SCI"

    Selected CI

    "FCI"

    Full CI

    "NONE"

    Default

  • TDHF= [logical] Default False

  • cosmo= [logical] Performs an implicit solvent job using COSMO model. Default False

  • subsystemEmbedding= [logical] Default False