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

An Examples of a MRSF-TDDFT Optimization calculation

[input]
system=
   O  -0.0000000000   0.0000000000  -0.0410615540
   H  -0.5331943294   0.5331943294  -0.6144692230
   H   0.5331943294  -0.5331943294  -0.6144692230
charge=0
functional=bhhlyp
basis=6-31g*
runtype=optimize
method=tdhf

[scf]
type=rohf
multiplicity=3

[tdhf]
type=mrsf
nstate=2

[optimize]
istate=1

[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: Set to optimize, indicating the goal is to perform a geometry optimization. This process iteratively adjusts the molecular geometry to find the structure that minimizes the system's total energy.

  • 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.

[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 calculation will consider two electronic states, likely including the ground state and the first excited state, allowing for an exploration of the molecule's electronic landscape.

[optimize] Section

  • istate: Specifies that the optimization is to be performed for the first excited state (istate=1, assuming the ground state is indexed as 0).

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