Introduction of Ab Initio Quantum Chemistry
Ab initio quantum chemistry is computational chemistry based on quantum chemistry, and it uses physical quantity (electron mass, Plank constant, and electric quantity) and atomic coefficient to strictly calculate the whole integral of the molecule. Ab initio methods are developed based on Born-Oppenheimer, single electron, and non-relativistic approximation which are the solution of the Schrödinger equation without any empirical parameters. The popular methods are Hartree-Fock methods, Post-Hartree-Fock methods, and Monte Carlo methods. Due to its theoretical rigor and accuracy, ab initio methods can be used in small molecules, macromolecules, static properties, and dynamic properties.
- Hartree-Fock methods
The Hartree-Fock method is a variational, wavefunction-based approach in which the electrons are considered as occupying single-particle orbitals making up the wavefunction. We use Hartree-Fock methods to solve the multi-particle problem and conduct crystal calculations.
- Post-Hartree-Fock methods
Various methods include Configuration Interaction (CI), Many-body Perturbation (MP) and Coupled Cluster (CC) are available in the Post-Hartree-Fock methods. We use Post-Hartree-Fock methods to capture the part of electron correlation missing in the original Hartree-Fock formulation.
- Monte Carlo methods
Our scientists have designed Monte Carlo methods for the application of the electronic structure of atoms and molecules. We use Monte Carlo methods to solve the quantum many-body problems such as the stationary Schrodinger equation by using the stochastic techniques for sampling the wave functions.
Scope of Applications
Ab initio methods have been applied to the high precision calculation of small molecular systems, quantitative calculation of medium molecular systems, and qualitative calculation of large molecular systems.
A diversity of molecular property including crystal structures, electronic bond structure, and lattice energy of molecular crystals can be calculated by ab initio methods. Multiple complex algorithms and high-quality database are available to support our prediction services. Apart from these, ab initio calculation of charge distribution, electrostatic potential, nonlinear optical properties, and thermochemical properties is attainable by our professional technical team.
- Materials properties prediction
Our computational teams can calculate, predict or design material structures and properties through creating theoretical models with ab initio methods. At Alfa Chemistry, metal-organic framework structures, new polymorphs, more efficient semiconductor materials, superconductors, nuclear materials, and two-dimensional functional materials can be predicted by ab initio methods.
Figure 1. Ab initio prediction of metal-organic framework structures (Darby, J.P.; et al. 2020)
- Catalytic chemistry
Catalytic reactions occupy a crucial position in chemistry. To find out the nature of chemical reactions, a wide range of experiments (such as possible intermediates, active catalysts, and routes) are tried one by one, which is energy-consuming and frequently of weak proof. To make up the experiments, ab initio methods based on the theoretical foundation can offer convincing information, such as photocatalytic reactions mechanisms, dominant transition states, and reactive intermediates.
- Biomedical research
1. Predictions of protein structures
We can predict protein secondary structure and advanced structure according to the amino acid sequence of proteins using ab initio methods. Based on the results of the secondary structure, structural type and fold type prediction, our experts further assemble the secondary structure with high credibility and build the final protein structure combined with stereochemistry, hydrophilic and hydrophobic properties, hydrogen bonding, and electrostatic interactions.
2. Predictions of gene structures
We establish the statistical model based on the structural characteristics of genes, and the gene structure is predicted only based on the gene sequences using ab initio methods. We adopt various ab initio prediction methods such as GENEMARK, GENSCAN, GENIE, HMMgene, GRAIL2, GeneParser, FGENEH, GeneKey, etc., to provide comprehensive prediction services.
Our ab initio methods for solving the problems of chemistry proceed as follows.
- Accuracy of calculation results
- Rapid calculation
- Comprehensive services of calculation
Ab initio methods are widely used in the calculation of molecular properties, catalytic reactions, functional materials properties, and biomedicine. We provide quick, excellent, and accurate services to meet your scientific research demands. If you are interested in our services, please feel free to contact us for more information.
- Yu, Q.; et al. Applications of calculation methods of quantum chemistry in field of chemistry calculation. Mater. Rep. 2009, 23: 21-26.
- Darby, J.P.; et al. Ab initio prediction of metal-organic framework structures. Chem. Mater. 2020, 32(13): 5835-5844.