PyQuante

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Molecule Objects

PyQuante programs use the Molecule object to contain the information about the molecule - the atoms, the charge, and the multiplicity. The syntax for Molecule is

>>> Molecule(name,atomlist,**opts)

The atomlist is a list of atomic numbers and a tuple with the x,y,z coordinates. Here's an example for constructing a molecule object for water:

>>> h2o=Molecule('h2o',[(8,(0,0,0)),(1,(1.0,0,0)),(1,(0,1.0,0))],units = 'Angstrom')

(of course the bond-angle is 90 degrees here, and is thus completely wrong, but this is only an example). Here's an example for the hydroxide ion that shows the use of the charge field:

>>> oh = Molecule('OH-',[(8,(0,0,0)),(1,(0.96,0,0))], units = 'Angstrom', charge=-1)

Here's an example for the NO molecule that shows the use of the multiplicity field

>>> no = Molecule('NO', [(7,(0,0,0)),(8,(2.12955,0,0))],multiplicity=2)

As of version 1.5.1, you may construct molecules using the atomic symbol instead of the atomic number, e.g.

>>> h2o=Molecule('h2o',[('O',(0,0,0)), ('H',(1.0,0,0)),('H',(0,1.0,0))],units = 'Angstrom')

Currently, the semiempirical code uses an extended verion of the Molecule object that adds a variety of additional features. Upcoming releases will hopefully unify the use of the Molecule between the HF, DFT, and semiempirical codes.