Editorial

This special issue of Molecular Physics was organised to commemorate the 13th National Quantum Chemistry Congress (NQCC) of China (8–11 June 2017, Dalian). Due to shortage of space, only a small number of authors were invited as representatives of the 1600 participants. Although the whole spectrum of theoretical and computational chemistry in China cannot fully be revealed here, one may get a rough idea on what are currently going on in the community.

Theoretical and computational chemistry in China can roughly be classified into three stages, the null stage before 1949, the building-up stage between 1950s and 1990s and the booming stage since late 1990s. This can be seen clearly from the expanding topics and growing numbers of participants of NQCC documented in Table 1. Roughly speaking, the Chinese pioneers in theoretical chemistry started with intramolecular rotations, ligand field theory, graph theory of conjugated molecular systems and semi-empirical molecular orbital theory between 1950s and 1980s, and continued with accurate treatment of few-body systems, valence bond theory, particle-hole symmetry-based configuration interaction, bonding rules of lanthanides and mechanisms of photochemical reactions between 1980s and 1990s. It is very unfortunate that one of the mainstreams of quantum chemistry, viz., development of many-body theories for electron correlation, was not picked up by the Chinese community during this period of time. Yet, theoretical and computational chemistry in China started to boom since the late 1990s, when the students of the pioneers came to play. They have much wider knowledge and have been contributing to essentially all the topics of modern theoretical chemistry, such as new relativistic many-electron Hamiltonians, new parametrisations of wave functions and density functionals, new approaches for quantum dynamics, quantum statistics, electronic/rovibrational spectroscopies of gaseous and condensed systems, new coarse-grained force fields and sampling techniques, efficient algorithms and software for large and extended systems, rational design of functional materials, massive applications and so on. Some of these developments are collected in this special issue.

Table 1. National quantum chemistry Congress of China.

			Number of
No.	Time	Location	participants	Main topics
1	December 1977	Shanghai	∼100	Ligand field theory, Hückel model, etc.
2	June 1983	Changchun	∼200	Extended Hückel model, CNDO, Xα, etc.
3	May 1987	Chengdu	∼200	CNDO, MNDO, Xα, etc.
4	October 1990	Jinan	∼300	Ab initio methods, classical and semi-classical trajectory methods, etc.
5	September 1993	Xiamen	∼300	Ab initio, valence bond, and semi-empirical methods, etc.
6	June 1996	Beijing	∼400	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, solids and surfaces, clusters, drug design, etc.
7	October 1999	Fuzhou	∼400	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, solids and surfaces, clusters, materials, drug design, etc.
8	July 2002	Changchun	∼550	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, solids and surfaces, clusters, materials, drug design, etc.
9	May 2005	Guilin	∼750	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, structures and functionalities of materials and biosystems, etc.
10	June 2008	Nanjing	∼900	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, structures and functionalities of materials and biosystems, etc.
11	May 2011	Hefei	∼1200	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, structures and functionalities of materials and biosystems, etc.
12	June 2014	Taiyuan	∼1400	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, structures and functionalities of materials and biosystems, etc.
13	June 2017	Dalian	∼1600	Quantum chemical methods, spectroscopies, chemical reactions and catalysis, structures and functionalities of materials and biosystems, etc.

In addition to the strong publications, the impact of the Chinese theoretical chemistry community can also be seen from the numerous international awards and honours, memberships in international academies and societies, and editorships of high-profile journals.