MRSF TDDFT Energy - Open-Quantum-Platform/openqp GitHub Wiki

An Examples of a MRSF-TDDFT Energy calculation

[input]
system=
   8   0.000000000   0.000000000  -0.041061554
   1  -0.533194329   0.533194329  -0.614469223
   1   0.533194329  -0.533194329  -0.614469223
charge=0
runtype=energy
basis=6-31g*
functional=bhhlyp
method=tdhf

[guess]
type=huckel

[scf]
multiplicity=3
type=rohf

[tdhf]
type=mrsf
nstate=3

[input] Section

  • system: This is the coordination of your system, your system's coordination can be achieved through two primary methods for OpenQP. The first method employs the Standard Cartesian format, as illustrated in the provided example. The second method utilizes the .XYZ format. To leverage the .XYZ format, save your coordination details in this format within your input folder, for instance, as H2O.xyz. Subsequently, it can be easily applied by specifying system=H2O.xyz in your input file. Here is an example of .XYZ format:
3
symmetry c1
O        0.000000000      0.000000000     -0.041061554
H       -0.533194329      0.533194329     -0.614469223
H        0.533194329     -0.533194329     -0.614469223

  • charge: The total charge of the system. A value of 0 indicates that the molecule is neutral, with no net charge.

  • runtype: Specifies the type of calculation. energy means that the computation aims to determine the electronic energy of the molecule without performing geometry optimization or calculating properties like gradients or Hessians.

  • basis: The basis set used for the calculation, 6-31gs in this case. The 6-31gs is a split-valence basis set with polarization functions on heavy atoms, designed to provide a good balance between accuracy and computational cost. You can find all of the basis-sets supported by OpenQP within the basis_set folder. Note that the basis-set file names are like 6-31g* -> 6-31g*, 6-31g** -> 6-31g(d,p) so there are no * at all.

  • functional: Specifies the DFT functional to be used. bhhlyp is a hybrid functional that combines Hartree-Fock exchange with B88 exchange and LYP correlation. It's known for its good performance in a variety of systems.

  • method: Indicates the computational method, tdhf for time-dependent Hartree-Fock.

[guess] Section

  • type: The initial guess for the molecular orbitals. huckel suggests using a simple Hückel molecular orbital (HMO) theory-based guess, which is particularly useful for π-conjugated systems but can serve as a starting point for various molecular systems.

[scf] Section

  • multiplicity: The multiplicity of the system, given by 2S+1 where S is the total spin angular momentum. A multiplicity of 3 suggests a triplet state (S=1), indicating unpaired electrons and a potentially open-shell configuration.

  • type: The SCF calculation type, rohf for Restricted Open-Shell Hartree-Fock. ROHF methods are used for molecules with open-shell electronic configurations, providing a way to handle both closed-shell (paired electrons) and open-shell (unpaired electrons) components of the wavefunction.

image

[tdhf] Section

  • type: The type of time-dependent calculation, mrsf for mixed-reference spin-flip. This advanced approach is designed to accurately describe excited states, particularly those involving changes in electron spin states. It allows for the treatment of systems where single-reference methods might fail, especially for complex excited-state phenomena.

  • nstate: The number of states for which the energy will be calculated, including the ground state. A value of 3 means the calculation will cover the ground state and two excited states, providing insight into the low-lying electronic excitations of the molecule.

MRSF-TDDFT Energy calculation log file

MRSF-TDDFT Energy calculation Molden file

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