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π bonds Calculation


π bonds are chemical bonds that are formed by the sidewise positive (same phase) overlap of atomic orbitals along a direction perpendicular to the internuclear axis. During the formation of π bonds, the axes of the atomic orbitals are parallel to each other whereas the overlapping is perpendicular to the internuclear axis. Prediction of number of π bonds and calculation of π bonds are vitally important tools for solving different kinds of problems regarding different chemical reactions.

Our Calculation Process

  • Structure optimization
  • π bonds analysis
  • π bonds calculation

Side-by-side overlap of each two p orbitals results in the formation of two π molecular orbitals.Figure 1. Side-by-side overlap of each two p orbitals results in the formation of two π molecular orbitals. Combining the out-of-phase orbitals results in an antibonding molecular orbital with two nodes. One contains the internuclear axis, and one is perpendicular to the axis. Combining the in-phase orbitals results in a bonding orbital. There is a node (blue plane) containing the internuclear axis with the two lobes of the orbital located above and below this node.

Our Services

At Alfa Chemistry, we apply a diversity of quantum methods to perform rapid calculation of π bonds by analyzing atomic orbital and bond energy. Our π bonds calculation services include the following:

  • The Quantum Theory of Atoms in Molecules (QTAIM), Energy Decomposition Analysis (EDA), and Natural Bond Orbital (NBO) approaches are applied to deepen the understanding of the nature of π bonds in some simple π -electron species.

  • We apply computational quantum chemistry to study the π bonds in different compounds. Our teams use Gaussian software to study the configuration, frequency, and interaction energy of the complex, analyze the electrostatic potential, and decompose the energy of all the complexes. Through NBO analysis, we can get the orbital, electronic layout, and electronic transfer situation.

  • At Alfa Chemistry, we also use Møller-Plesset disturbance theory perturbation theory of the second order (MP2), and coupling cluster models such as CCSD and CCSD(T) to assess the interaction energy of the optimal structure, which is important for the accurate π bonds calculation.

  • When it is necessary to accurately describe p-p π bond, p-d π bond and d-d π bond in a weak interaction system, a very large basis set is needed to accurately evaluate the polarization effect. Therefore, we introduce a large number of polarization and dispersion functions into the basis set. Our scientists use complete basis set (CBS) or correlation-consistent basis set and construct them in a systematic way.

  • Charge decomposition analysis (CDA) is developed based on the fragment orbital method, which proposes to decompose the charge transfer between molecular fragments into different orbitals. We use CDA to draw the orbital interaction diagram to gain a deeper understanding of charge transfer, and determine the π bond.

  • Extended Transition State - Natural Orbitals for Chemical Valence (ETS-NOCV) method has been widely used in the research of different types of systems and is most commonly used to investigate the chemical bonding between fragments. Our experts use this orbital composition analysis method to calculate the composition of each atom in the orbital and π bonds.

π bonds calculation provides an effective way to optimize the chemical process. Our π bonds calculation services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!


  • Molecular Orbital (MO) Theory (Review). Chemistry LibreTexts. 2020.

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