In Fig. 5c, we explore the 2D potential enthalpy surface along the two symmetry-lowering parameters by evaluating the relative enthalpies of structures that are intermediate between those of the III and VIII phases, characterised by specific partially rotated NH4 groups as well as F ion displacemen...
Any structure for which the enthalpy of formation lies on the convex hull is by definition thermodynamically stable and - in principle - can be synthesized experimentally53,54. References 1. Kaesz, H. D. & Saillant, R. B. Hydride complexes of the transition metals. Chem. Rev. 72, 231–...
For thermometry in high-enthalpy air, Spearrin et al. [115] validated and demonstrated a sensor based on NO detection at pressures up to ≈150 atm in a shock tube using a quantum-cascade laser near 5.2 μm [115]. This sensor inferred the temperature by comparing the measured concentration...
When placed in a cube a tetrahedral methane molecule can retain its symmetry only if it its hydrogens point toward four corners of the cube. In the phases studied here such an orientation introduces unfavorable steric interactions, and a lower enthalpy can be obtained when the hydrogens point t...
Calculations on the AgF2 system indicate that Pnma and Pbcn polymorphs become nearly degenerate in terms of enthalpy above 50 GPa [37]. We do find for CuF2 that Pbcn is more stable than Pnma below 64 GPa (see Figure 6a), but at this pressure both are less stable than the Pca21 ...
Keywords: boron nitride; phase diagram; advanced materials; high pressure 1. Introduction Boron nitride (BN) was first synthesized in the mid-nineteenth century in hexagonal form (hBN, Figure 1a) [1], and a century later became a commercial product widely employed as powder (e.g., a ...
1A and B, both two phases have the same coplanar zigzag HF chains and their stacking styles are different while Pnma phase is denser and have volumetric gain (PV-term in the enthalpy) at high pressure. In our calculation, Pnma phase can stabilize thermodynamically at least to 1 TPa. ...
What is the molar enthalpy of vaporization (Delta H_{vap}) for carbon disulfide in kJ mol? What is the vapor pressure of carbon disulf Determine if the given system is work done by the surroundings on the system? Assume pressure and temperature are constan...
The high-pressure behavior were explored by merging the evolutionary algorithm and ab initio total energy calculations, as implemented in the USPEX code. Enthalpy and electronic structure calculation were carried out by using the Vienna ab initio Simulation Package within the framework of GGA (Perdew–...
The latter are defined as those compounds for which any possible decomposition reaction is accompanied by a free energy (which at T = 0 K reduces to enthalpy) increase. In most cases, binary phase diagrams are targeted, for the large number of possible stoichiometries in a ternary...