At the core of RevQCMagic are Configurations and States. Together these describe an entire system.

Take ground-state H<sub>2</sub> with electronic configuration (1s)<sup>2</sup>, and ground-state HeH<sup>+</sup> also with electronic configuration (1s)<sup>2</sup>. These two systems have different Configuration, but the same State.

Now consider ground-state H<sub>2</sub> with electronic configuration (1s)<sup>2</sup> and H<sub>2</sub><sup>+</sup> with electronic configuration (1s)<sup>1</sup>. These two systems have the same Configuration, but different State.

==Configuration==
A single Configuration object contains various SubConfigurations, such as geometry or basis set used etc. Configuration objects also keep track of the State objects they are associated with.

==SubConfiguration==

===Geometry===

===ConvolvedBasisSet===

==State==

==[[RevQCMagic|Return]]==

Configurations and States

2026-03-30T21:22:16Z

Jst55: /* Configuration */

Creating a QChem Input File

2026-03-30T21:08:00Z

Jst55: /* Building Configuration and QChemMetadata Manually */

__TOC__

==Summary==
RevQCMagic has an in-built QChem input file writer. The writer uses three things to generate an input file:
* Configuration (The Configuration object contains all information which gives a state context, i.e. it contains the nuclei involved, the geometry of the nuclei, the basis set for each atom, etc)
* MetaData (For a QChem input file this is a QChemMetadata object which contains all of the calculation parameters.)
* FilePath (The filepath to save the input file to.)

==Example: Building Configuration and QChemMetadata Manually==
<pre>
from qcmagic.core.cspace.configurationspace import Configuration
from qcmagic.core.cspace.molecule.atom import Atom
from qcmagic.core.cspace.molecule.atomfragment import AtomFragment
from qcmagic.core.cspace.molecule.geometry import Geometry
from qcmagic.auxiliary.linearalgebra3d import Vector3D
from qcmagic.auxiliary.qcmagic_standards import ANGSTROM_TO_BOHR

from qcmagic.interfaces.input_writers.qchem_input_writer.qchem_input_writer import (
QChemMetadata,
QChemInputWriter,
)

import numpy as np

def generate_H2_STO3G_Qchem_input_files():
# Each input file will have the same calculation parameters
parameters = {
'job_type': 'sp',
'basis': 'STO-3G',
'method': 'HF',
'symmetry_ignore': 'true',
'scf_convergence': '11',
'thresh': '14',
'unrestricted': 'false',
'iqmol_fchk': 'true',
'max_scf_cycles': '500',
'mem_total': '5976800'
}

# Create a QChemMetadata object to store the calculation parameters
# as well as the total charge (0) and the multiplicity (2*spin_proj+1)
metadata = QChemMetadata()
metadata.update_from_dictionary(parameters)
metadata.state_properties = {"total_charge": 0, "spin_projection": 0}

# Considering H-H bond lengths from 0.2 to 2,1 Angstroms
for radius in np.linspace(0.2, 2.1, 20):
# RevQCMagic uses Bohr whereas QChem uses Angstroms
radius_bohr = radius * ANGSTROM_TO_BOHR

# Every new geometry requires a new Configuration
config = Configuration()

# Generate a co-ordinate system for holding the molecule geometry
coordsystem = AtomFragment(parent=None)
H2 = AtomFragment(coordsystem)

# Add the two hydrogen atoms, note the required use of Vector3D
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, -radius_bohr/2])))
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, +radius_bohr/2])))

# Turn the AtomFragment object into a Geometry SubConfiguration, then
# add to the total Configuration
config.add_subconfiguration(Geometry([(None, None)], H2))

# Generate the input file writer using the Configuration, and use the
# QChemMetadata to write the specific input file to the specified filepath.
# If wanted to do different calculations on the same Configuration then could
# create different QChemMetadata objects and call the writer with each of them.
writer = QChemInputWriter(config)
filepath = f'H2_STO-3G_radius_{radius:.1f}A.inp'
writer(filepath, metadata)

generate_H2_STO3G_Qchem_input_files()
</pre>

The above code generates input files which all look like the one given below.

<pre>
$molecule
0 1
H +0.00000000000000 +0.00000000000000 -0.10000000000000
H +0.00000000000000 +0.00000000000000 +0.10000000000000
$end
$rem
basis STO-3G
job_type sp
method hf
symmetry_ignore true
scf_convergence 11
thresh 14
unrestricted false
iqmol_fchk true
max_scf_cycles 500
mem_total 5976800
$end
</pre>

==[[RevQCMagic|Return to RevQCMagic]]==

Creating a QChem Input File

2026-03-30T21:07:47Z

Jst55: /* Example: Generating QChem Input Files for Different H-H Bond Lengths */

__TOC__

==Summary==
RevQCMagic has an in-built QChem input file writer. The writer uses three things to generate an input file:
* Configuration (The Configuration object contains all information which gives a state context, i.e. it contains the nuclei involved, the geometry of the nuclei, the basis set for each atom, etc)
* MetaData (For a QChem input file this is a QChemMetadata object which contains all of the calculation parameters.)
* FilePath (The filepath to save the input file to.)

==Building Configuration and QChemMetadata Manually==
<pre>
from qcmagic.core.cspace.configurationspace import Configuration
from qcmagic.core.cspace.molecule.atom import Atom
from qcmagic.core.cspace.molecule.atomfragment import AtomFragment
from qcmagic.core.cspace.molecule.geometry import Geometry
from qcmagic.auxiliary.linearalgebra3d import Vector3D
from qcmagic.auxiliary.qcmagic_standards import ANGSTROM_TO_BOHR

from qcmagic.interfaces.input_writers.qchem_input_writer.qchem_input_writer import (
QChemMetadata,
QChemInputWriter,
)

import numpy as np

def generate_H2_STO3G_Qchem_input_files():
# Each input file will have the same calculation parameters
parameters = {
'job_type': 'sp',
'basis': 'STO-3G',
'method': 'HF',
'symmetry_ignore': 'true',
'scf_convergence': '11',
'thresh': '14',
'unrestricted': 'false',
'iqmol_fchk': 'true',
'max_scf_cycles': '500',
'mem_total': '5976800'
}

# Create a QChemMetadata object to store the calculation parameters
# as well as the total charge (0) and the multiplicity (2*spin_proj+1)
metadata = QChemMetadata()
metadata.update_from_dictionary(parameters)
metadata.state_properties = {"total_charge": 0, "spin_projection": 0}

# Considering H-H bond lengths from 0.2 to 2,1 Angstroms
for radius in np.linspace(0.2, 2.1, 20):
# RevQCMagic uses Bohr whereas QChem uses Angstroms
radius_bohr = radius * ANGSTROM_TO_BOHR

# Every new geometry requires a new Configuration
config = Configuration()

# Generate a co-ordinate system for holding the molecule geometry
coordsystem = AtomFragment(parent=None)
H2 = AtomFragment(coordsystem)

# Add the two hydrogen atoms, note the required use of Vector3D
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, -radius_bohr/2])))
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, +radius_bohr/2])))

# Turn the AtomFragment object into a Geometry SubConfiguration, then
# add to the total Configuration
config.add_subconfiguration(Geometry([(None, None)], H2))

# Generate the input file writer using the Configuration, and use the
# QChemMetadata to write the specific input file to the specified filepath.
# If wanted to do different calculations on the same Configuration then could
# create different QChemMetadata objects and call the writer with each of them.
writer = QChemInputWriter(config)
filepath = f'H2_STO-3G_radius_{radius:.1f}A.inp'
writer(filepath, metadata)

generate_H2_STO3G_Qchem_input_files()
</pre>

The above code generates input files which all look like the one given below.

<pre>
$molecule
0 1
H +0.00000000000000 +0.00000000000000 -0.10000000000000
H +0.00000000000000 +0.00000000000000 +0.10000000000000
$end
$rem
basis STO-3G
job_type sp
method hf
symmetry_ignore true
scf_convergence 11
thresh 14
unrestricted false
iqmol_fchk true
max_scf_cycles 500
mem_total 5976800
$end
</pre>

==[[RevQCMagic|Return to RevQCMagic]]==

Creating a QChem Input File

2026-03-30T21:06:16Z

Jst55:

__TOC__

==Summary==
RevQCMagic has an in-built QChem input file writer. The writer uses three things to generate an input file:
* Configuration (The Configuration object contains all information which gives a state context, i.e. it contains the nuclei involved, the geometry of the nuclei, the basis set for each atom, etc)
* MetaData (For a QChem input file this is a QChemMetadata object which contains all of the calculation parameters.)
* FilePath (The filepath to save the input file to.)

==Example: Generating QChem Input Files for Different H-H Bond Lengths==
<pre>
from qcmagic.core.cspace.configurationspace import Configuration
from qcmagic.core.cspace.molecule.atom import Atom
from qcmagic.core.cspace.molecule.atomfragment import AtomFragment
from qcmagic.core.cspace.molecule.geometry import Geometry
from qcmagic.auxiliary.linearalgebra3d import Vector3D
from qcmagic.auxiliary.qcmagic_standards import ANGSTROM_TO_BOHR

from qcmagic.interfaces.input_writers.qchem_input_writer.qchem_input_writer import (
QChemMetadata,
QChemInputWriter,
)

import numpy as np

def generate_H2_STO3G_Qchem_input_files():
# Each input file will have the same calculation parameters
parameters = {
'job_type': 'sp',
'basis': 'STO-3G',
'method': 'HF',
'symmetry_ignore': 'true',
'scf_convergence': '11',
'thresh': '14',
'unrestricted': 'false',
'iqmol_fchk': 'true',
'max_scf_cycles': '500',
'mem_total': '5976800'
}

# Create a QChemMetadata object to store the calculation parameters
# as well as the total charge (0) and the multiplicity (2*spin_proj+1)
metadata = QChemMetadata()
metadata.update_from_dictionary(parameters)
metadata.state_properties = {"total_charge": 0, "spin_projection": 0}

# Considering H-H bond lengths from 0.2 to 2,1 Angstroms
for radius in np.linspace(0.2, 2.1, 20):
# RevQCMagic uses Bohr whereas QChem uses Angstroms
radius_bohr = radius * ANGSTROM_TO_BOHR

# Every new geometry requires a new Configuration
config = Configuration()

# Generate a co-ordinate system for holding the molecule geometry
coordsystem = AtomFragment(parent=None)
H2 = AtomFragment(coordsystem)

# Add the two hydrogen atoms, note the required use of Vector3D
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, -radius_bohr/2])))
H2.add(Atom('H', H2, Vector3D([0.00, 0.00, +radius_bohr/2])))

# Turn the AtomFragment object into a Geometry SubConfiguration, then
# add to the total Configuration
config.add_subconfiguration(Geometry([(None, None)], H2))

# Generate the input file writer using the Configuration, and use the
# QChemMetadata to write the specific input file to the specified filepath.
# If wanted to do different calculations on the same Configuration then could
# create different QChemMetadata objects and call the writer with each of them.
writer = QChemInputWriter(config)
filepath = f'H2_STO-3G_radius_{radius:.1f}A.inp'
writer(filepath, metadata)

generate_H2_STO3G_Qchem_input_files()
</pre>

The above code generates input files which all look like the one given below.

<pre>
$molecule
0 1
H +0.00000000000000 +0.00000000000000 -0.10000000000000
H +0.00000000000000 +0.00000000000000 +0.10000000000000
$end
$rem
basis STO-3G
job_type sp
method hf
symmetry_ignore true
scf_convergence 11
thresh 14
unrestricted false
iqmol_fchk true
max_scf_cycles 500
mem_total 5976800
$end
</pre>

==[[RevQCMagic|Return to RevQCMagic]]==

Configurations and States

2026-03-30T21:02:37Z

Jst55:

2026-03-30T17:02:59Z

Jst55: Created page with "==Quick Guides== Creating a QChem Input File ==Core Concepts== Configurations and States"

==Quick Guides==
[[Creating a QChem Input File]]

==Core Concepts==
[[Configurations and States]]

Main Page

2026-03-30T17:01:15Z

Jst55: /* Software Tutorials */

Main Page

2026-03-30T17:01:07Z

Jst55: /* Software Tutorials */