Experimental evidence for glass polymorphism in vitrified water droplets

The nature of amorphous ices has been debated for more than 35 years. In essence, the question is whether they are related to ice polymorphs or to liquids. The fact that amorphous ices are traditionally prepared from crystalline ice via pressure-induced amorphization has made a clear distinction tricky. In this work, we vitrify liquid droplets through cooling at ≥106 K ⋅ s−1 and pressurize the glassy deposit. We observe a first order–like densification upon pressurization and recover a high-density glass. The two glasses resemble low- and high-density amorphous ice in terms of both structure and thermal properties. Vitrified water shows all features that have been reported for amorphous ices made from crystalline ice. The only difference is that the hyperquenched and pressurized deposit shows slightly different crystallization kinetics to ice I upon heating at ambient pressure. This implies a thermodynamically continuous connection of amorphous ices with liquids, not crystals.

Evaluation of automated particle picking for cryogenic electron microscopy using high-precision transmission electron microscope simulation based on a multi-slice method

This work describes the GRIPS automated particle-picking software for cryogenic electron microscopy and the evaluation of this software using elbis, a high-precision transmission electron microscope (TEM) image simulator. The goal was to develop a method that can pick particles under a small defocus condition where the particles are not clearly visible or under a condition where the particles are exhibiting preferred orientation. The proposed method handles these issues by repeatedly performing three processes, namely extraction, two-dimensional classification and positioning, and by introducing mask processing to exclude areas with particles that have already been picked. TEM images for evaluation were generated with a high-precision TEM image simulator. TEM images containing both particles and amorphous ice were simulated by randomly placing O atoms in the specimen. The experimental results indicate that the proposed method can be used to pick particles correctly under a relatively small defocus condition. Moreover, the results show that the mask processing introduced in the proposed method is valid for particles exhibiting preferred orientation. It is further shown that the proposed method is applicable to data collected from real samples.

Effect of Hydrophobic Silicon Substrate on the Ice Formation at Different Temperatures

In this work, we investigate the effect of silicon substrate and temperature on the ice formation through molecular dynamics simulations. It was found that silicon substrate accelerates the ice formation rate. Depending on the temperatures of the systems, the formation rate can be accelerate or decelerated. The obtained results showed that, as the temperature increased from the lowest temperature 100K to the highest temperature 220K, the number of water molecules transformed into ice decreased. We found that the hydrophobic property of silicon is not a barrier for approaching ice formation. The high correlation between Si and the hydrogen atoms of water molecules stimulated the ice formation on the surface of silicon and allowed the formation of amorphous ice directly on the surface of silicon. The temperature effect on ice formation was in distinguishing two different behaviors one from 100K to 180K and the second above 180K. These behaviors were related to the temperature of which amorphous ice is stable. The results of the average number of hydrogen bonds and their lifetime are in parallel with the results of the number density profiles that can best explain how silicon affects the ice formation. The coordination number of water molecules increased with the decrease of the temperature for silicon substrate which means that bigger ice clusters were found. The ice molecules, which were formed near the silicon substrate, are more recognized than that of the bulk. To better understand these effects, bulk systems were used as comparative systems.

Cosmology, astrobiology and the RNA world: just add quintessential water

Laboratory generation of water nanoclusters from amorphous ice and strong terahertz (THz) radiation from water nanoclusters ejected from water vapour into a vacuum suggest the possibility of water nanoclusters ejected into interstellar space from abundant amorphous ice-coated cosmic dust produced by supernovae explosions. Water nanoclusters (section ‘Water nanoclusters’) offer a hypothetical scenario connecting major mysteries of our Universe: dark matter (section ‘Baryonic dark matter’), dark energy (section ‘Dark energy’), cosmology (section ‘Cosmology’), astrobiology (section ‘Astrobiology’) and the RNA world (section ‘The RNA world’) as the origin of life on Earth and habitable exoplanets. Despite their expected low density in space compared to hydrogen, their quantum-entangled diffuse Rydberg electronic states make cosmic water nanoclusters a candidate for baryonic dark matter that can also absorb, via the microscopic dynamical Casimir effect, the virtual photons of zero-point-energy vacuum fluctuations above the nanocluster cut-off vibrational frequencies, leaving only vacuum fluctuations below these frequencies to be gravitationally active, thus leading to a possible common origin of dark matter and dark energy. This picture includes novel explanations of the small cosmological constant, the coincidence of energy and matter densities, possible contributions of the red-shifted THz radiation from cosmic water nanoclusters at redshift z ≅ 10 to the cosmic microwave background (CMB) spectrum, the Hubble constant crisis, the role of water as a known coolant for rapid early star formation and ultimately, how life may have originated from RNA protocells on Earth and exoplanets and moons in the habitable zones of developed solar systems. Together, they lead to a cyclic universe cosmology – based on the proposed equivalence of cosmic water nanoclusters to a quintessence scalar field – instead of a multiverse based on cosmic inflation theory. Recent CMB birefringence measurements may support quintessence. Finally, from the quantum chemistry of water nanoclusters interacting with prebiotic organic molecules, amino acids and RNA protocells on early Earth and habitable exoplanets, this scenario is consistent with the anthropic principle that our Universe must have those properties which allow life, as we know it – based on water, to develop at the present stage of its history.

The impact of temperature and unwanted impurities on slow compression of ice

For slowly compressed hexagonal ice pressure-induced amorphisation to high-density amorphous ice (HDA) takes place below and at 130 K, but polymorphic transformation to ice IX at 140–170 K. Stable ice...

On the spectral features of dangling bonds in CH4/H2O amorphous ice mixtures

Dangling bond bands of pure H2O and CH4/H2O ice mixtures are studied at density functional theory levels. Agreement with experiments on frequency shifts and intensity enhancements of infrared dangling bond bands was found.