title: Relativistic Effects Break Periodicity in Group 6 Diatomic Molecules.
abstract: The finding of the periodic law is a milestone in chemical science. The periodicity of light elements in the Periodic Table is fully accounted for by quantum mechanics. Here we report that relativistic effects change the bond multiplicity of the group 6 diatomic molecules M2 (M = Cr, Mo, W, Sg) from hextuple bonds for Cr2, Mo2, W2 to quadruple bonds for Sg2, thus breaking the periodicity in the nonrelativistic domain. The same trend is also found for other superheavy-element diatomics Rf2, Db2, Bh2, and Hs2.
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University , Beijing 100084, China.
authors.forename: Yi-Lei
authors.initials: YL
authors.lastname: Wang
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University , Beijing 100084, China.
authors.forename: Han-Shi
authors.initials: HS
authors.lastname: Hu
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University , Beijing 100084, China.
authors.forename: Wan-Lu
authors.initials: WL
authors.lastname: Li
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University , Beijing 100084, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Wei
authors.affiliation: Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University , Beijing 100084, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li