The compressibility crystals usually depends on their structure. Under hydrostatic pressure most crystals shrink in all directions (so called all-positive compression). There are also materials expanding along one direction (negative linear compressibility) or along a plane (negative area compressibility). These features can be usually explained by the structural and molecular features of crystals.[1,2] However, for the porous materials also the pressure-transmitting medium is important and the phenomenon of compression cannot be confined to the crystal structure only. Also other external parameters must be taken into account. It can be shown that such materials can drastically change their compression in different liquids [3]. Even the fundamental law of the positive volume compression (dV/dp > 0) appears to be questionable [4]. The presence of pores can be pressure-dependent [5]. The compression can be additionally complicated by structural transformations and topochemical reactions stimulated by the pressure [6].
This study was supported by project OPUS 10 UMO-2015/19/B/ST5/00262 from the Polish National Science Centre.
References
[1] W. Cai, A. Katrusiak, Giant negative linear compression positively coupled to massive thermal expansion in a metal–organic framework, Nature Commun, 5 (2014) Article number: 4337
[2] W. Cai, J. He, W. Li, A. Katrusiak, Anomalous Compression of a Weakly CH∙∙∙O Bonded Nonlinear Optical Molecular Crystal, J. Mater. Chem. C, 2 (2014) 6471–6476. DOI: 10.1039/C4TC00654B
[3] W. Cai, A. Gładysiak, M. Anioła, V. J. Smith, L. J. Barbour, A. Katrusiak, Giant negative area compressibility tunable in a soft porous framework material, J. Am. Chem. Soc. 137 (2015) 9296−9301.
[4] S. Sobczak, A. Katrusiak, Zone-Collapse Amorphization Mimicking the Negative Compressibility of a Porous Compound, Cryst. Growth Des. 18 (2018) 1082-1089.
[5] P. A. Guńka, K. F. Dziubek, A. Gładysiak, M. Dranka, J. Piechota, M. Hanfland, A. Katrusiak, J. Zachara, Compressed arsenolite As4O6 and its helium clathrate As4O6∙2He, Cryst. Growth Des. 15 (2015) 3740−3745.
[6] A. Półrolniczak, S. Sobczak, A. Katrusiak, Solid-State Associative Reactions and the Coordination Compression Mechanism, Inorg. Chem. 57 (2018) 8942-8950. DOI: 10.1021/acs.inorgchem.8b00913