Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs.
Negative linear compressibility (NLC) is a relatively uncommon phenomenon and rarely studied in organic systems. Here we provide the direct evidence of the persistent NLC in organic mineral ammonium oxalate monohydrate under high pressure using synchrotron X-ray powder diffraction, Raman spectroscopy and density functional theory (DFT) calculation. Synchrotron X-ray powder diffraction measurement reveals that ammonium oxalate monohydrate shows both positive and negative linear compressibility along b-axis before 11.5 GPa. The red shift of the external Raman modes and abnormal changes of several selected internal modes in high-pressure Raman spectra further confirmed the NLC. DFT calculations demonstrate that the N-H···O hydrogen bonding "wine-rack" motifs result in the NLC along b-axis in ammonium oxalate monohydrate. We anticipate the high-pressure study of ammonium oxalate monohydrate may represent a promising strategy for accelerating the pace of exploitation and improvement of NLC materials especially in organic systems.
†State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Yuancun
Y
Qiao
†State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Kai
K
Wang
†State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Hongsheng
H
Yuan
‡Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201203, China.
Ke
K
Yang
†State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Bo
B
Zou
Negative linear compressibility (NLC); computational methodology; hydrogen bonds; organic mineral; wine-rack motif