Central Variables
In ORBKIT, all central variables are extracted from quantum chemistry outputs
(cf. orbkit.read
) and organized within the class
orbkit.qcinfo.QCinfo
. The corresponding command reads:
from orbkit import read
qc = read.main_read('h2o.md',itype='molden')
This class stores all the information required for subsequent
computations and is organized as follows:
Member 
Type 
Shape/Members 
qc.geo_info 
numpy.ndarray (dtype= str ) 
(N_{atoms}, 3) 
qc.geo_spec 
numpy.ndarray (dtype= str ) 
(N_{atoms}, 3) 
qc.ao_spec 
list of dict 
“pnum”, “atom”, “type”, “coeffs”, (“exp_list”) 
qc.ao_spherical 
list of tuple 
(N_{spherical AOs}, 2) 
qc.mo_spec 
list of dict 
“energy”, “occ_num”, “sym”, “coeffs” 
qc.geo_info: 
 Contains information about the atoms and is only required for the creation
of the output file.
 The three columns correspond to
 Atom symbol
 Atom number (according to the input file)
 Nuclear charge (if present in the input file)

qc.geo_spec: 
 Contains the atom positions in units of Bohr radii.
 The three columns correspond to the x, y, and zcoordinates.

qc.ao_spec: 
 Contains all information about the atomic orbitals
 The number of dictionaries corresponds to the number of contracted Gaussians
 Members of the dictionaries:
 “atom”
 Atom number (according to the input file, i.e., starting from 1) (
int )
 “coeffs”
 1st element exponent and 2nd element contraction coefficients of
the basis functions
numpy.ndarray (dtype= float ) with the shape (N_{primitives}, 2)
 “pnum”
 Number of number of primitives (
int )
 “exp_list” (optional)
 Exponents of the basis functions
 Only present if the order of the exponents deviate from the standard
molden order
list of tuple , i.e., [(l_x1,l_y1,l_z1), (l_x2,l_y2,l_z2), ...]

qc.ao_spherical: 

 Contains the order of the spherical harmonic basis functions within the
input file
list of tuple , i.e., [(l_1,m_1), (l_2,m_2), ...] with
the angular momentum quantum number m and the magnetic quantum number
l

qc.mo_spec: 
 Contains all information about the molecular orbitals.
 The number of dictionaries corresponds to number of molecular orbitals
 Members of the dictionaries:
 “coeffs”
 Molecular orbital coefficients
numpy.ndarray (dtype= float ) with the shape (N_{AO}, 1)
 “energy”
 Energy of molecular orbital (
float )
 “occ_num”
 Occupation of molecular orbital (
float )
 “sym”
 MOLPROlike symmetry label of molecular orbital (
str ), e.g.,
“12.1” or “12.A1”

Besides those central variables, the orbkit.qcinfo.QCinfo
class possess
additional members which are not of importance for the computations done by
ORBKIT.