pseudopotential

This option defines the pseudopotentials used for quantum chemistry calculations. You can define pseudopotentials in several flexible ways.

Warning

pseudopotential only contains pseudopotential and does not contain any valence electron basis set information. You must assign basis sets in basis. The valence basis and core pseudopotential must match.

Below is a typical example. H is represented by a def2-TZVP basis set. For Au, the valence electrons are represented by a def2-TZVP basis set, and core electrons are repesented by def2-ecp, i.e. Stuggart-Cologne pseudopotential.

basis
  def2-TZVP
end
pseudopotential
  def2-ecp
end
# The Karlsruhe basis sets for Au was developed with Stuggart-Cologne pseudopotential.
mol
    Au 0. 0. 0.  # SDD+def2-TZVP
    H  0. 0. 1.  # def2-TZVP
end

If you write it in this way:

# A wrong input!
basis
  def2-TZVP
end
mol
    Au 0. 0. 0.
    H  0. 0. 1.
end

Then, no pseudopotential is applied for any element!

Also, keep in mind that the valence basis and core pseudopotential must match. The following combinations are usually accepted:

Valence Basis Set	Pseudopotential
def2-X	def2-ecp
(aug-)cc-X-pp	cc-ecp
lanlX	lanl-ecp

Using Built-in Pseudopotentials

A lot of important pseudopotentials have been provided in a folder pseudopotential in the same path of Qbics. The files are named after their names well-known in computational chemistry community. For example, pseudopotential/def2-ecp contains the Stuggart-Cologne pseudopotentials. All files are named in small cases.

To use them, simple write down the basis set name. It is case-insensitive. For example, to use def2-ecp:

pseudopotential
  def2-ecp
end

Qbics will extract pseudopotential information from pseudopotential/def2-ecp for all atoms that have pseudopotentials. For example, you molecule contains only C, H, N, Ce, and F. Since in pseudopotential/sdd, there is only pseudopotential for Ce, then for C, H, N, and F, no pseudopotentials are applied.

Explicit Pseudopotential Definitions

You can also explicitly define your pseudopotentials. For example, you want to apply pseudopotentials for Rb and Sr, then their pseudopotentials can be defined in this way:

pseudopotential
  RB     0
  RB-ECP     3     28
  f POTENTIAL
        1
  2      3.84311400          -12.31690000
  s-f POTENTIAL
        3
  2      5.03655100           89.50019800
  2      1.97084900            0.49376100
  2      3.84311400           12.31690000
  p-f POTENTIAL
        3
  2      4.25834100           58.56897400
  2      1.47070900            0.43179100
  2      3.84311400           12.31690000
  d-f POTENTIAL
        3
  2      3.02312700           26.22489800
  2      0.65038300            0.96283900
  2      3.84311400           12.31690000
  ****
  SR     0
  SR-ECP     3     28
  f POTENTIAL
        1
  2      4.63397500          -15.80599200
  s-f POTENTIAL
        3
  2      7.40007400          135.47943000
  2      3.60637900           17.53446300
  2      4.63397500           15.80599200
  p-f POTENTIAL
        3
  2      6.48486800           88.35970900
  2      3.28805300           15.39437200
  2      4.63397500           15.80599200
  d-f POTENTIAL
        3
  2      4.62284100           29.88898700
  2      2.24690400            6.65941400
  2      4.63397500           15.80599200
  ****
end

The pseudopotential definition is of standard Gaussian94 format:

• The definition of the pseudopotential for each atom ends with 4 asterisks, i.e. ****.

• The definition starts with the element name like Rb and a 0. Currently 0 has no meaning.

• Then, three parameters are given: pseudopotential name, maximum angular momentum, and number of core electrons.

• Then, the semi-local pseudopotential and local ones are listed. Each pseudopotential has the form \(\sum_{k=1}^{K}d_{kl}r^{n_{kl}}e^{-\xi_{kl}r^2}\):

  • The first line is a comment.

  • The contraction degree \(K\).

  • Then, each line defines the power \(n_{kl}\) , the exponent \(\xi_{kl}\), and the contraction coefficient \(d_{kl}\). They are 3 real numbers.

Hint

Note that many pseudopotentials in Gaussian94 format can be obtained from https://www.basissetexchange.org/. But, remember to replace D to E since the former is not recognized by Qbics. Also, add **** between elements.

Using Self-defined Pseudopotential Files

You can also put your explicit pseudopotential definitions into some files, say /home/zhang/userdef/my-own-pseudopotential. Qbics will automatically read it if you give explicit file name including path.

pseudopotential
  /home/zhang/userdef/my-own-pseudopotential
end