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Historically high-pressure (HP) research has been an area that is heavily dependent on the availability of the experimental equipment. Many of the discoveries in HP science followed promptly from breakthroughs in instrumentation development, which provided researchers with higher pressure limits or larger sample volumes. A limited availability of commercial pressure cells and the need to remain at the cutting edge of the research make it likely that anyone working in this field will at some point engage in designing new or in modifying existing HP equipment. This presentation aims to introduce an engineering approach to developing pressure cells and to present such generic tools as computer aided design (CAD) and finite element analysis (FEA). The use of engineering methods in the design of HP equipment will be illustrated using recently developed pressure cells. This includes some new devices for neutron scattering such as gas-driven sapphire anvil pressure cell for changing pressure at cryogenic temperatures in neutron diffraction experiments [1]. Another example is a gas loader for the P-E press which can be used to load gases into the sample space at elevated pressures for subsequent studies of gases and gas mixtures as well as for use of gases as pressure-transmitting media to pressures of over 18 GPa [2]. The examples of use of FEA for miniaturization of the pressure cells and their components will include miniature pressure cells for X-ray diffraction with cryo-flow refrigerators shown in the Figure below [3].
abstracts
Since the discovery of Single-Molecule Magnets (SMMs) in 1993 there has been extensive interest in understanding, developing and tuning the nature of magnetic interactions within SMMs with the intention of gaining greater insight into the nature of these interactions.[1] Typically this is done synthetically using variations in ligand geometry and co-ordination environment to vary magnetic behaviour. More recently it has been demonstrated that high hydrostatic pressure are also an effective mechanism for "tuning" properties such as magnetic susceptibility in a variety of SMMs.[2] The number of studies utilising high hydrostatic pressure to investigate molecular magnetism is extremely limited due to their inherent difficulty however we report a new study investigating the pressure tunabilty of Re(IV) based SMMs. 4d and 5d metal ions such as Re are of interest due their enhanced magnetic exchanges relative to their 3d analogues and Re(IV) based complexes are of particular interest. Previous studies into [ReX6]2- (X = Cl, Br and I) anions demonstrate significant antiferromagnetic coupling, not transmitted through chemical interactions but rather through weak Re-X...X interactions in the solid state which may be easily perturbed at high pressure. [3] Therefore we report an investigation into the tunability of magnetic susceptibility in a variety of [ReX4] based compounds using high pressure magnetic susceptibility measurements and correlate the results with structure observations taken from high pressure single crystal X-ray diffraction experiments. The effects of the removal of solvent trapped in the lattice using temperature and vacuum and the corresponding effect on magnetic behaviour and chemical structure are also reported.
