Computational chemical software is an important bridge connecting experiment and theory. The development of computational chemical software is both a scientific and engineering problem. My main interest is to develop new methods for realistic chemical problems and implement it with state-of-the-art software engineering and scientific numerical computation techniques, offering chemists highly efficient yet easy-to-use tools. Some of my works are listed below.

ABCluster: The most successful software for conformation search of molecules, global optimization of chemical clusters, and fast structure generation

Manual location of the most stable conformation of molecules and isomer of clusters is costly and error-prone work. ABCluster, the most successful conformation search and global optimization software, has become a powerful tool for chemists from a broad range of fields. Actually, in computational atmospheric chemistry, ABCluster has become a standard tool. Besides its efficiency, it is also highly easy to use. ABCluster can be used to investigate chemical objects from atomic clusters, molecular clusters, ligated clusters, surface-supported clusters, flexible organic molecules, host-guest complexes, to even zeolite, MOFs, protein-drug complexes, peptide-DNA and membranes!

Computerized Code Optimization: Evaluation of Molecular Integrals

The evaluation of molecular integrals is necessary part for all quantum chemistry software. Among various kinds of integrals, the electron-nuclear attraction integrals (EANs) and electron repulsion integrals (ERIs) are the most important factor determining the efficiency of a quantum chemistry software. The EAN and ERI evaluation involves complicated and lengthy recurrence relations and in practice, a large number of memory operations and floating-point operations. It is very difficult for manually written codes to reach maximum efficiency. Thus, automatic code generation technique, i.e., "using codes to write codes", is used. For EANs and ERIs of all angular momentum combination from (s|s) to (g|g), from (ss|ss), (ps|ss) to (gg|gf), (gg|gg), the recurrence relations are analyzed by the tree-search algorithm. Also, common subexpression elimination, cache access optimization, etc. are applied to optimize the program, and finally, more than 100,000 lines of efficient codes are generated. This is how the molecular integral evaluation library libreta is designed.

Labile Capping Bond, Hydration of Lanthanide(III)

Trivalent lanthanide cations (Ln3+) have large radii, resulting a high coordination number in solvent or complexes. An interesting property of Ln3+ is that the water exchange rate exhibits a peak curve: it increases from La to Gd and decreases from Gd to Lu (Chem. Rev. 2005, 105, 1923). This has puzzled investigators for a long time. During 2013 to 2014, I find that in Ln3+complexes, the capping ligands can be inherently labile due to the hindrance, perhaps being "shorter and weaker", which I called "labile capping bond" (Inorg. Chem. 2014, 53, 7700, J. Phys. Chem. A 2015, 119, 774). It can successfully explain the peak curve and a series of hydration phenomena of Ln3+. This has been applied in the estimation of hydration exchange rate (J. Phys. Chem. A 2015, 119, 6436). In 2017, people has confirmed this by the NRM experiments of some Gd complexes (Chem. Eur. J. 2017, 23, 1110).

Linear Scaling Coupled Cluster Theory, Incremental Scheme

Incremental scheme is an efficient and accurate approach for computing the energies by the CCSD, CCSD(T) methods and their F12 variants for large closed- and open-shell molecules. It can reduce the comptuational cost with little loss of accuracy. For molecular clusters the efficiency is much more higher. This approach has been applied to several chemical problems, like the hydration energies of lanthanide(III), energy difference of isomers of organic molecules, solvent extraction, etc.