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scf

scf

Defines how to perform a self-consistent field (SCF) calculation.

charge

Define the total charge of the system.

Value An integer
Default 0
spin2p1
Value An integer
Default 1 for systems with an even number of electrons.
2 for systems with an odd number of electrons.

Define the spin multiplicity of the system, i.e., 2S+1, where S is the spin of the system. For example, to consider singlet and triplet states, set spin2p1 to 1 and 3, respectively.

spin2p1 can be either positive or negative. Both values represent the same spin multiplicity, but they determine which type of orbital is occupied first in an SCF wave function: alpha or beta. For instance, for a system with 11 electrons and spin2p1 = 1, there will be 6 alpha and 5 beta electrons (alpha filled first). If spin2p1 = -1, there will be 5 alpha and 6 beta electrons (beta filled first).

For systems with an odd number of electrons, use a negative spin2p1 to occupy beta orbitals first.For example:

In this case, the molecule will have 2 alpha electrons and 0 beta electrons. For another input:
The molecule will have 2 beta electrons and 0 alpha electrons.
type

For singlet states, both restricted and unrestricted SCF are available. Unrestricted SCF is very useful in treating spin-polarized systems. For non-singlet states, only the unrestricted one can be used.

Value R for restricted SCF (alpha and beta orbitals are restricted to be identical)
U for unrestricted SCF (alpha and beta orbitals are not necessarily identical)
Default R for singlet state
U for other states
max_it

Define the maximum number of SCF iterations.

Value A non-negative integer
Default 128
Hint

You can set max_it to 0 to perform a non-iterative calculation.


energy_cov

Define the energy convergence threshold for SCF calculations.

Value A real number
Default 1.E-6
density_cov

Define the density matrix convergence threshold for SCF calculations.

Value A real number
Default 1.E-8
Hint

The SCF calculation is considered converged when both the energy and density convergence conditions are satisfied.


nodiis

Do not use the Direct Inversion of the Iterative Subspace (DIIS) convergence acceleration algorithm.

print_MO

Print the molecular orbital coefficients. Without this option, only the molecular orbital energies and occupations will be printed.

schwarz

Define the Schwarz screening tolerance. All two-electron integral contributions smaller than this value will be discarded to accelerate the calculation. A positive real number is required.

Value A real number
Default 1.E-10
Warning

Do not set the value too large (e.g., 1.E-5), as it may lead to incorrect results.


do_tso

Instead of performing ordinary SCF, use target state optimization (TSO) SCF. This method is powerful for calculating excited and diabatic states. For theoretical details, please refer to:

Tutorials of using TSO-DFT can be found here: