研究目的
To perform an exhaustive study of compressibility and structural changes of [Cu4I4{PPh2(CH2CH=CH2)}4] under high pressure up to 5 GPa, determine the isothermal equation of state, and confirm the existence of a phase transition around 2.3 GPa.
研究成果
The study confirms an isostructural phase transition of second order at 2.3 GPa in [Cu4I4{PPh2(CH2CH=CH2)}4], characterized by molecular rearrangement and distortion of the cubane cluster. The bulk modulus is around 10 GPa, typical for organometallic compounds, with anisotropic compression behavior. The combination of experimental and computational methods provides robust support for these findings, highlighting the importance of high-quality single crystal data in high-pressure studies.
研究不足
Limitations include the opening angle of the diamond anvil cell restricting data collection to 40-60% of reflections compared to full datasets, potential non-hydrostatic conditions if pressure exceeds hydrostatic limits, and the inability of ab initio simulations to fully reproduce anomalous behavior above 2.3 GPa due to complexities in weak intermolecular interactions.
1：Experimental Design and Method Selection:
Combined high-pressure single crystal X-ray diffraction experiments and ab initio simulations based on density functional theory were used to study the compound under pressure up to 5 GPa at 298 K. The rationale was to leverage the precision of single crystal diffraction over powder diffraction for accurate structural analysis.
2：Sample Selection and Data Sources:
A single crystal of Cu4I4{PPh2(CH2CH=CH2)}4 was synthesized according to Perruchas et al. and confirmed by X-ray diffraction at ambient conditions. High-pressure measurements were conducted at the High Pressure Endstation of the MSPD beamline in ALBA synchrotron.
3：List of Experimental Equipment and Materials:
Diamond anvil cell (Diacell Bragg-Mini from Almax-EasyLab), synchrotron beamline (MSPD at ALBA), detector (Rayonix SX165 CCD), pressure transmitting medium (methanol-ethanol-water mixture 16:3:1), ruby chip for pressure calibration, and software (CrysAlisPro, SHELXL, EosFit7-GUI).
4：Experimental Procedures and Operational Workflow:
The single crystal was placed in a diamond anvil cell with a hydrostatic pressure medium. Pressure was applied and measured using ruby fluorescence. X-ray diffraction data were collected by rotating the cell and processed using CrysAlisPro software. Structures were refined with SHELXL.
5：Data Analysis Methods:
Data were analyzed to determine cell parameters, bond lengths, angles, and volume changes. The Birch-Murnaghan equation of state was fitted using EosFit7-GUI. Ab initio simulations were performed with VASP software using DFT with GGA-PBE and van der Waals corrections.
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