scholarly journals Phase Stability of Chloroform and Dichloromethane at High Pressure

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 920
Author(s):  
Dominik Kurzydłowski ◽  
Taisiia Chumak ◽  
Jakub Rogoża
Keyword(s):  
High Pressure ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Raman Band ◽  
Ambient Pressure ◽  
Experimental Information ◽  
Model Systems ◽  
Dipole Interactions ◽  
Metastable Structure ◽  
The Stability

Chloroform (CHCl3) and dichloromethane (CH2Cl2) are model systems for the study of intermolecular interactions, such as hydrogen bonds and halogen–halogen interactions. Here we report a joint computational (density-functional perturbation theory (DFPT) modelling) and experimental (Raman scattering) study on the behaviour of the crystals of these compounds up to a pressure of 32 GPa. Comparing the experimental information on the Raman band positions and intensities with the results of calculations enabled us to characterize the pressure-induced evolution of the crystal structure of both compounds. We find that the previously proposed P63 phase of CHCl3 is in fact a metastable structure, and that up to 32 GPa the ambient-pressure Pnma structure is the ground state polymorph of this compound. For CH2Cl2 we confirm the stability of the ambient-pressure Pbcn structure up to 32 GPa. We show that the high-pressure evolution of the crystal geometry of CHCl3 in the Pnma structure is a result of the subtle balance between dipole–dipole interactions, hydrogen bonds and Cl···Cl contacts. For CH2Cl2 (Pbcn structure) the dipole–dipole interactions and hydrogen bonds are the main factors influencing the pressure-induced changes in the geometry.

scholarly journals Pressure-induced phase transitions in Na2B12H12, structural investigation on a candidate for solid-state electrolyte

2019 ◽  
Vol 75 (3) ◽  
pp. 406-413 ◽  
Author(s):  
Romain Moury ◽  
Zbigniew Łodziana ◽  
Arndt Remhof ◽  
Léo Duchêne ◽  
Elsa Roedern ◽  
...  
Keyword(s):  
High Pressure ◽  
Solid State ◽  
Bulk Modulus ◽  
Density Functional ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
Ionic Conductors ◽  
Theoretical Predictions ◽  
Primary Order ◽  
The Stability

closo-Borates, such as Na2B12H12, are an emerging class of ionic conductors that show promising chemical, electrochemical and mechanical properties as electrolytes in all-solid-state batteries. Motivated by theoretical predictions, high-pressure in situ powder X-ray diffraction on Na2B12H12 was performed and two high-pressure phases are discovered. The first phase transition occurs at 0.5 GPa and it is persistent to ambient pressure, whereas the second transition takes place between 5.7 and 8.1 GPa and it is fully reversible. The mechanisms of the transitions by means of group theoretical analysis are unveiled. The primary-order parameters are identified and the stability at ambient pressure of the first polymorph is explained by density functional theory calculations. Finally, the parameters relevant to engineer and build an all-solid-state battery, namely, the bulk modulus and the coefficient of the thermal expansion are reported. The relatively low value of the bulk modulus for the first polymorph (14 GPa) indicates a soft material which allows accommodation of the volume change of the cathode during cycling.

scholarly journals High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 910
Author(s):  
Daniel Diaz-Anichtchenko ◽  
Robin Turnbull ◽  
Enrico Bandiello ◽  
Simone Anzellini ◽  
Daniel Errandonea
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

A DFT-D study on the stability and intramolecular interactions of the salts of 1,2,3- and 1,2,4-triazoles

2014 ◽  
Vol 92 (11) ◽  
pp. 1111-1117
Author(s):  
Xueli Zhang ◽  
Xuedong Gong
Keyword(s):  
Hydrogen Bonds ◽  
Density Functional ◽  
Energy Gap ◽  
Lattice Energy ◽  
Intramolecular Interactions ◽  
Dispersion Energy ◽  
Functional Theory ◽  
Formation Reaction ◽  
The Stability ◽  
Intramolecular Hydrogen

Nitrogen-rich 1,2,4-triazole (1) and 1,2,3-triazole (2) react as bases with the oxygen-rich acids HNO3 (a), HN(NO2)2 (b), and HClO4 (c) to produce energetic salts (1a, 1b, and 1c and 2a, 2b, and 2c, respectively) potentially applicable to composite explosives and propellants. In this study, these salts were studied with the dispersion-corrected density functional theory. For the isomers such as 1a and 2a, the more negative ΔrGm of the formation reaction leads to a higher thermally stable salt. The ability to form intramolecular hydrogen bonds predicted with the quantum theory of atoms in molecules has the order of 2 > 1. Different hydrogen bonds result in different second-order perturbation energies, redshifts in IR, and electron density differences. The charge transfer, binding energy, dispersion energy, lattice energy, and energy gap between frontier orbits in the salts of 1 are larger than those of 2, which is helpful for stabilizing the former, and 1 is more obviously stabilized than 2 by formation of salts. Different conformations of 1 and 2 hardly affect the frontier orbital distributions. Base 1 is a more preferred base than 2 to form salts.

A new high-pressure benzocaine polymorph — towards understanding the molecular aggregation in crystals of an important active pharmaceutical ingredient (API)

2020 ◽  
Vol 76 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Ewa Patyk-Kaźmierczak ◽  
Michał Kaźmierczak
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Ambient Pressure ◽  
Active Pharmaceutical Ingredient ◽  
Molecular Packing ◽  
Molecular Aggregation ◽  
Pressure Release ◽  
Hydrogen Bonding Pattern

Benzocaine (BZC), an efficient and highly permeable anaesthetic and an active pharmaceutical ingredient of many commercially available drugs, was studied under high pressure up to 0.78 GPa. As a result, new BZC polymorph (IV) was discovered. The crystallization of polymorph (IV) can be initiated by heating crystals of polymorph (I) at a pressure of at least 0.45 GPa or by their compression to 0.60 GPa. However, no phase transition from polymorph (I) to (IV) was observed. Although polymorph (IV) exhibits the same main aggregation motif as in previously reported BZC polymorphs (I)–(III), i.e. a hydrogen-bonded ribbon, its molecular packing and hydrogen-bonding pattern differ considerably. The N—H...N hydrogen bonds joining parallel BZC ribbons in crystals at ambient pressure are eliminated in polymorph (IV), and BZC ribbons become positioned at an angle of about 80°. Unfortunately, crystals of polymorph (IV) were not preserved on pressure release, and depending on the decompression protocol they transformed into polymorph (II) or (I).

scholarly journals Crystal structures and dynamical properties of dense CO2

2016 ◽  
Vol 113 (40) ◽  
pp. 11110-11115 ◽  
Author(s):  
Xue Yong ◽  
Hanyu Liu ◽  
Min Wu ◽  
Yansun Yao ◽  
John S. Tse ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Theoretical Calculations ◽  
Ambient Pressure ◽  
Md Simulations ◽  
Ab Initio Molecular Dynamics ◽  
Structural Polymorphism ◽  
Stability Structure ◽  
Dynamical Properties ◽  
The Stability

Structural polymorphism in dense carbon dioxide (CO2) has attracted significant attention in high-pressure physics and chemistry for the past two decades. Here, we have performed high-pressure experiments and first-principles theoretical calculations to investigate the stability, structure, and dynamical properties of dense CO2. We found evidence that CO2-V with the 4-coordinated extended structure can be quenched to ambient pressure below 200 K—the melting temperature of CO2-I. CO2-V is a fully coordinated structure formed from a molecular solid at high pressure and recovered at ambient pressure. Apart from confirming the metastability of CO2-V (I-42d) at ambient pressure at low temperature, results of ab initio molecular dynamics and metadynamics (MD) simulations provided insights into the transformation processes and structural relationship from the molecular to the extended phases. In addition, the simulation also predicted a phase V′(Pna21) in the stability region of CO2-V with a diffraction pattern similar to that previously assigned to the CO2-V (P212121) structure. Both CO2-V and -V′ are predicted to be recoverable and hard with a Vicker hardness of ∼20 GPa. Significantly, MD simulations found that the CO2 in phase IV exhibits large-amplitude bending motions at finite temperatures and high pressures. This finding helps to explain the discrepancy between earlier predicted static structures and experiments. MD simulations clearly indicate temperature effects are critical to understanding the high-pressure behaviors of dense CO2 structures—highlighting the significance of chemical kinetics associated with the transformations.

High Pressure Properties of Superconducting Material Palladium

2013 ◽  
Vol 813 ◽  
pp. 327-331
Author(s):  
Wei Min Peng ◽  
Zhong Li Liu ◽  
Hong Zhi Fu
Keyword(s):  
High Pressure ◽  
Perturbation Theory ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Density Functional ◽  
High Pressures ◽  
Ambient Pressure ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Density Functional Perturbation Theory

The electronic and the superconducting properties of Pd were studied in the framework of density functional perturbation theory. We explored the superconducting transition temperature for bulk Pd and predicted possible superconductivity at ambient and high pressures. It is found that of Pd is 0.0356 K at ambient pressure and it decreases with pressure.

scholarly journals Superconductivity in Materials under Extreme Conditions: An ab-initio Prediction from Density Functional Theory

2021 ◽  
Author(s):  
Thiti Bovornratanaraks ◽  
Prutthipong Tsuppayakorn-aek
Keyword(s):  
Density Functional Theory ◽  
High Pressure ◽  
Ab Initio ◽  
Crystal Structures ◽  
Density Functional ◽  
Ambient Pressure ◽  
Extreme Conditions ◽  
Functional Theory ◽  
Novel Structure ◽  
And Performance

The relation between thermodynamically stable and electronic structure preparation is one of the fundamental questions in physics, geophysics and chemistry. Since the discovery of the novel structure, this has remained as one of the main questions regarding the very foundation of elemental metals. Needless to say this has also bearings on extreme conditions physics, where again the relation between structure and performance is of direct interest. Crystal structures have been mainly at ambient conditions, i.e. at room temperature and ambient pressure. Nevertheless it was realized early that there is also a fundamental relation between volume and structure, and that this dependence could be most fruitfully studied by means of high pressure experimental techniques. From a theoretical point of view this is an ideal type of experiment, since only the volume is changed, which is a very clean variation of the external conditions. Therefore, at least in principle, the theoretical approach remains the same irrespective of the high pressure loading of the experimental sample. Theoretical modeling is needed to explain the measured data on the pressure volume relationships in crystal structures. Among those physical properties manifested itself under high pressure, superconductivity has emerged as a prominent property affected by pressure. Several candidate structure of materials are explored by ab initio random structure searching (AIRSS). This has been carried out in combination with density functional theory (DFT). The remarkable solution of AIRSS is possible to expect a superconductivity under high pressure. This chapter provide a systematically review of the structural prediction and superconductivity in elemental metals, i.e. lithium, strontium, scandium, arsenic.

Theoretical studies on the structure and properties of DAT/BTNAT cocrystal under high pressure

2020 ◽  
Vol 98 (3) ◽  
pp. 128-133
Author(s):  
Liangyu Li ◽  
Weihua Zhu
Keyword(s):  
High Pressure ◽  
Structural Transformation ◽  
Density Functional ◽  
Hydrostatic Compression ◽  
Theoretical Studies ◽  
Dispersion Correction ◽  
Structure And Properties ◽  
Absorption Properties ◽  
Functional Theory ◽  
The Stability

The structural, electronic, and absorption properties of 3,5-diamino-1H-1,2,4-triazole (DAT) and 5,5′-bis(trinitromethyl)-3,3′-azo-1H-1,2,4-triazole (BTNAT) cocrystal under hydrostatic compression of 0–100 GPa were investigated by using periodic density functional theory with dispersion correction (DFT-D). The results indicate that a structural transformation occurred at 25 GPa. The structural transformation makes the positions of the molecules rearrange in the cocrystal and improves the stability and planarity. An analysis of the band gap and density of states indicates that the DAT/BTNAT cocrystal becomes more sensitive under compression. The absorption spectra illustrate that the DAT/BTNAT cocrystal has relatively high optical activity with the increasing pressure. Our work may offer some valuable information for understanding the behavior of energetic cocrystals under high pressure.

Density functional theory study of the stability of the tetrabutylphosphonium and tetrabutylammonium montmorillonites

Clay Minerals ◽  
2019 ◽  
Vol 54 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Eva Scholtzová ◽  
Daniel Tunega
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Dynamic Properties ◽  
Organic Cations ◽  
Structure Stability ◽  
Functional Theory ◽  
Interatomic Distances ◽  
Principle Density Functional Theory ◽  
The Stability

AbstractThe stability of organoclays prepared from smectites and organic cations depends on the type of used cation, among other factors. This study provides a prediction of the structure, stability and dynamic properties of organoclays based on montmorillonite (Mt) intercalated with two types of organic cations – tetrabutylammonium (TBA) and tetrabutylphosphonium (TBP) – using first-principle density functional theory. The results obtained from simulations were also used in the interpretation of the experimental infrared spectrum of the TBP-Mt organoclay. Analysis of interatomic distances showed that weak C–O···H hydrogen bonds were important in the stabilization of both TBA- and TBP-Mt models, with slightly stronger hydrogen bonds for the TBP cation. Calculated intercalation and adsorption reaction energies (ΔEint//ΔEads*/ΔEads**) confirmed that TBP-Mt structures (–72.4//–32.8/–53.8 kJ/mol) were considerably more stable than TBA-Mt structures (–56.7//–22.6/–37.4 kJ/mol). The stronger interactions of the alkyl chains of the TBP cation with Mt basal surfaces in comparison to those of the TBA cation were also correlated with the positions of the calculated bands of the C–H stretching vibrations.

scholarly journals Hexamer formation in tertiary butyl alcohol (2-methyl-2-propanol, C4H10O)

2006 ◽  
Vol 62 (4) ◽  
pp. 599-605 ◽  
Author(s):  
Pamela A. McGregor ◽  
David R. Allan ◽  
Simon Parsons ◽  
Stewart J. Clark
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Phase Ii ◽  
Density Functional ◽  
Ambient Pressure ◽  
Chair Conformation ◽  
Butyl Alcohol ◽  
Tertiary Butyl Alcohol ◽  
Tertiary Butyl ◽  
Phase Iv

The crystal structure of phase II of tertiary butyl alcohol (2-methyl-2-propanol, C4H10O) has been solved using a combination of single-crystal X-ray diffraction techniques and ab initio density functional calculations. This trigonal P\overline 3 phase, which is stable at both low temperature and high pressure, and the triclinic P\overline 1 phase (phase IV) have very similar enthalpies, the calculations revealing only a 3.859 kJ mol−1 enthalpy difference at ambient pressure, despite the substantial change of the intermolecular bonding motif from helical catemer to hexamer with an increase in pressure or reduction in temperature. The hexamers in the trigonal phase adopt a chair conformation. There are two unique hexamers: at low temperature these are centred at (0, 0, 1\over2) and (2\over3, 1\over3, 0.961 (13)), and at high pressure the centres are (0, 0, 1\over2) and (2\over3, 1\over3, 0.958 (14)). A slight flattening of the hexamers is observed at high pressure and the calculations confirm that phase II becomes more stable relative to phase IV on pressure increase.

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