Peierls-distorted monoclinic MnB(4) with a Mn-Mn bond.

Area of Science:

• Solid State Chemistry
• Materials Science
• Crystallography

Background:

• Tetraborides of chromium and manganese possess unique boron frameworks resembling tetragonal diamond.
• These materials are anticipated to exhibit exceptional hardness.

Purpose of the Study:

• To grow single crystals of manganese tetraboride (MnB4).
• To elucidate the crystal structure and electronic properties of MnB4.

Main Methods:

• Single crystal growth of MnB4.
• X-ray crystallography for structure determination.
• (11)B Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy.
• Density Functional Theory (DFT) calculations.
• Magnetic susceptibility measurements.

Main Results:

• MnB4 crystallizes in the monoclinic system (space group P21/c) with four distinct boron sites.
• An unusually short Mn-Mn distance suggests a double bond, attributed to Peierls distortion.
• DFT calculations indicate Mn(I) centers and paramagnetism, consistent with magnetic measurements.
• A pseudo-band gap at the Fermi energy was observed, indicating semiconducting behavior.

Conclusions:

• The synthesized MnB4 exhibits a novel crystal structure with potential for advanced material applications.
• The observed semiconducting behavior opens avenues for exploring its electronic functionalities.