While chemical bonds usually determine the structure and properties of a material, bonds between neighboring metal atoms can also change as temperature or other conditions change. These changes can lead to unusual electronic and magnetic behaviors.
A new study on Li₀.₅VS₂ shows that bonding between vanadium atoms can reorganize as the material passes through successive structural changes. The study was led by Assistant Professor Keita Kojima from the Graduate School of Environment, Life, Natural Science and Technology, Okayama University, Japan, along with Professor Naoyuki Katayama from Okayama University. The study was made available online on August 24, 2026, in the journal Chemistry of Materials .
An early study by Dr. Donald W. Murphy and his co-workers showed that Li₀.₅VS₂ was the only composition that exhibited two distinct magnetic phase transitions, whereas only a single transition was observed for cases where the values of x were 0, 0.33, and 1. This unusual behavior strongly motivated Dr. Kojima to investigate the electronic and structural changes associated with these transitions. "Li₀.₅VS₂ stood out as the only composition exhibiting two distinct magnetic phase transitions, whereas only a single transition was observed for cases where the values of x were 0, 0.33, and 1. This unusual behavior strongly motivated us to investigate the electronic and structural changes associated with these transitions," explained Dr. Kojima.
The researchers identified two successive magnetic phase transitions, occurring near 345 and 140 K. At high temperatures, the vanadium atoms have a triangular arrangement. At intermediate temperatures, they form zigzag chains, while the material develops a more localized magnetic response. At low temperatures, the vanadium atoms shift again, and their bonds reorganize, accompanied by a sharp decrease in magnetic response.
Importantly, electrical resistivity measurements showed that the compound remains metallic through all three phases. The intermediate-temperature phase is particularly unusual because it combines electrical conductivity with a more localized magnetic response.
Structural measurements helped explain this behavior. In the intermediate-temperature phase, some vanadium atoms move closer together to form zigzag chains. The V–V distances shorten by about 0.2 Å, indicating that the atoms begin to form bonds. However, there are not enough electrons to completely fill all of these bonds. Calculations indicate that these electron-deficient σ bonds are only partially occupied. This unusual bonding allows V–V bonds to form while the material remains electrically conductive.
At low temperatures, the zigzag chains break up into more localized V–V pairs, known as dimers. The change in bonding is accompanied by a sharp drop in magnetic response, indicating that the localized magnetic moments present at intermediate temperatures are almost completely suppressed. However, the material remains metallic because some electrons continue to move through vanadium orbitals that do not fully participate in the dimer bonds.
Computer calculations further helped explain these changes. Electron–electron interactions help stabilize the V–V dimers at low temperatures, while Hund's coupling contributes to the magnetic response of the intermediate-temperature phase. Together, the results connect the material's magnetic behavior with changes in how its electrons participate in bonding.
The findings show that chemical bonding can play an active role in shaping the properties of correlated materials. In Li₀.₅VS₂, electron-deficient V–V bonds reorganize as the material responds to temperature, producing successive changes in its structure and magnetic behavior while preserving metallic conductivity.
This provides a new design principle for quantum and functional materials in which chemical bonding itself could be used to control electronic and magnetic properties. "In the longer term, if the bonding states and transition temperatures can be controlled by chemical composition, elemental substitution, or pressure, the underlying mechanism could provide a basis for materials whose electrical and magnetic properties can be switched in multiple steps. Such materials may be relevant to future sensors, switching devices, and other responsive functional materials," Dr. Kojima explained.
Overall, this study shows that unusual metal–metal bonds can reorganize in successive stages as the material is cooled, producing major changes in its structure and magnetic behaviors while it continues to conduct electricity. The findings provide a framework for understanding how different bonding arrangements can give rise to competing electronic states in correlated materials.
Reference
Title of original paper: Competing Electron-Deficient σ-Bond Configurations across Successive Structural Transitions in Li0.5VS2
Journal: Chemistry of Materials
DOI: https://doi.org/10.1021/acs.chemmater.6c01358
About Okayama University, Japan
As one of the leading universities in Japan, Okayama University aims to create and establish a new paradigm for the sustainable development of the world. Okayama University offers a wide range of academic fields, which become the basis of the integrated graduate schools. This not only allows us to conduct the most advanced and up-to-date research, but also provides an enriching educational experience.
Website: https://www.okayama-u.ac.jp/index_e.html
About Assistant Professor Keita Kojima from Okayama University, Japan
Dr. Keita Kojima is a researcher and Assistant Professor in the Department of Physics at the Graduate School of Environmental, Life, Natural Science and Technology at Okayama University in Japan. He graduated from the Department of Physics, School of Engineering at Nagoya University in March 2019, and completed his master's program in applied physics at the Nagoya University Graduate School of Engineering in March 2021. His research primarily focuses on quantum structural physics in correlated electronic materials, seeking to understand how a material's microscopic atomic structure influences its quantum electronic properties. He has published 17 high cited articles till date.
Funding information
This work was supported by the Grant-in-Aid for Scientific Research (Grant Nos. JP17K17793, JP20H01849, JP20H02604, JP21K18599, JP21J21236, JP22KJ1521, JP23H04104, JP23K03286, JP24H01620, JP24K01329, JP26H00590, JP26H00599, JJP26K00019, JP26K00023, JP26K07021, and JP26K17087) and the Japan Science and Technology Agency (JST) COI-NEXT Programme (Grant No. JPMJPF2221).
