Computational chemistry was initially developed based on quantum mechanical methodologies, but it proved impossible to study large systems, such as large biologic macromolecules. This prompted the development of molecular mechanics where systems are described at the atomic level using empirical force fields. Nonetheless, methods based on force fields have severe problems that are well known. For example, these methods cannot describe the rich coordination chemistry of transition metals and the requirement of parametrization limits their applicability. There is clearly a need to develop new computational methods based on quantum mechanics that study large and heterogeneous systems. Quantum based methods are typically limited by the calculation of 2-electron integrals and diagonalization of large matrices. Following our recent work on the fast calculation of 2-electron integrals and diagonalization of large matrices, a new generation of semi-empirical methods for biologic simulations, materials science and drug-design is being developed. It is based on a highly parameterized tight-binding Hamiltonian and incorporates ab initio electron-electron repulsions and electron-nucleus attractions. This will guarantee that the method will be generic and applicable to a wide range of systems. The current work on the development of a computer library for the fast computation of 2-electron integrals will be presented. The integration of ab initio electron-electron and nucleus-electron integrations on a semi-empirical Hamiltonian will also be detailed. The numerical accuracy of the approximated methodology will be discussed, and results will be compared with existing methodologies, for example methods based on Rys polynomials. Furthermore, initial applications on large fullerenes and smaller benchmark systems will be described.

Renaissance of semi-empirical methods: Fast computation of 2-electron integrals

254th National Meeting (2017)

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