Abstract
The full crystal structure of the phyllosilicate mineral tuperssuatsiaite, including the positions of the hydrogen atoms in its unit cell, is determined for the first time by using first-principles solid-state methods. From the optimized structure, its infrared spectrum and elastic properties are determined. The computed infrared spectrum is in excellent agreement with the experimental spectrum recorded from a natural sample from Ilímaussaq alkaline complex (Greenland, Denmark). The elastic behavior of tuperssuatsiaite is found to be extremely anomalous and significant negative compressibilities are found. Tuperssuatsiaite exhibits the important negative linear compressibility phenomenon under small anisotropic pressures applied in a wide range of orientations of the applied strain and the very infrequent negative area compressibility phenomenon under external isotropic pressures in the range from 1.9 to 2.4 GPa. The anisotropic negative linear compressibility effect in tuperssuatsiaite is related to the increase of the unit cell along the direction perpendicular to the layers charactering its crystal structure. The isotropic negative area compressibility effect, however, is related to the increase of the unit cell dimensions along the directions parallel to the layers.
Highlights
The compressibility is a fundamental material property measuring the change of the dimensions of a given material with respect to pressure
Some of the most important negative linear compressibility (NLC) mechanisms are the presence of ferroelastic instabilities, phonon instabilities, ferroelastic phase transitions and the anomalous mechanical behavior found in some materials displaying correlated polyhedral tilts and helical and wine-rack structural motifs
The Fourier-transform infrared (FTIR) spectrum of tuperssuatsiaite was recorded by the attenuated total reflection (ATR) method with a diamond cell on a Nicolet iS5 spectrometer
Summary
The compressibility is a fundamental material property measuring the change of the dimensions of a given material with respect to pressure. The NLC phenomena has an enormous number of important potential applications, such as the development of ultrasensitive pressure detectors, robust shock-absorbing composites, pressure-driven actuators, optical telecommunication cables, artificial muscles, generation body armor and devices for biomedical applications.[2,3,9,22,23,24] Synthetic and design approaches have been developed to obtain materials with improved mechanical performance.[4,9,25,26,27] the number of natural and man-made NLC materials known so far is limited and, for these materials, the magnitude of the negative compressibility and the range of external pressures for which these phenomena are displayed are too small to be widely exploitable in practice
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