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

An Examples of a 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=bbhlyp
method=tdhf

[guess]
type=huckel

[scf]
multiplicity=1
type=rhf

[tdhf]
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 use of the b3lyp5 functional, a widely used hybrid functional in DFT calculations that combines local and non-local exchange-correlation effects. The B3LYP functional is known for its general applicability and good performance across a wide range of molecular 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: A multiplicity of 1 indicates a singlet state, which is typical for the ground state of most closed-shell molecules, including water. Multiplicity is defined as 2S+1, where S is the total spin angular momentum quantum number.

  • type: The rhf (Restricted Hartree-Fock) method is used for the SCF calculations, suitable for closed-shell or singlet state molecules where all electrons are paired.

image

[tdhf] Section

  • 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.

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