Entrapped Transient Chloroform Solvates of Bilastine

The knowledge about the solid forms landscape of Bilastine (BL) has been extended. The crystal structures of two anhydrous forms have been determined, and the relative thermodynamic stability among the three known anhydrous polymorphs has been established. Moreover, three chloroform solvates with variable stoichiometry have been identified and characterized, showing that S3CHCl3-H2O and SCHCl3 can be classified as transient solvates which transform into the new chloroform solvate SCHCl3-H2O when removed from the mother liquor. The determination of their crystal structures from combined single crystal/synchrotron X-ray powder diffraction data has allowed the complete characterization of these solvates, being two of them heterosolvates (S3CHCl3-H2O and SCHCl3-H2O) and SCHCl3 a monosolvate. Moreover, the temperature dependent stability and interrelation pathways among the chloroform solvates and the anhydrous forms of BL have been studied.

Theoretical study on the stability and aromaticity in silapentafulvenes towards triplet ground state species

Aromaticity and bond dissociation energy are the origin of the relative thermodynamic stability of silapentafulvenes and their isomers.

Polymorphism of Bulk Boron Nitride

Boron nitride (BN) is a material with outstanding technological promise because of its exceptional thermochemical stability, structural, electronic and thermal conductivity properties, and extreme hardness. Yet, the relative thermodynamic stability of its most common polymorphs (diamond-like cubic and graphite-like hexagonal) has not been resolved satisfactorily because of the crucial role played by kinetic factors in the formation of BN phases at high temperatures and pressures (experiments), and by competing bonding, electrostatic and many-body dispersion forces in BN cohesion (theory). This lack of understanding hampers the development of potential technological applications, and challenges the boundaries of fundamental science. Here, we use high-level first-principles theories that correctly reproduce all important electronic interactions (the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation) to estimate with unprecedented accuracy the energy differences between BN polymorphs, and thus overcome the accuracy hurdle that hindered previous theoretical studies. We show that the ground-state phase of BN is cubic and that the frequently observed two-dimensional hexagonal polymorph becomes entropically stabilized over the cubic at temperatures slightly above ambient conditions (Tc = 63+-20'C). We also reveal a new low-symmetry monoclinic phase that is extremely competitive with the other low-energy polymorphs and which could explain the origins of the experimentally observed ``compressed h--BN'' phase. Our theoretical findings therefore should stimulate new experimental efforts in bulk BN as well as promote the use of high-level theories in modelling of technologically relevant van der Waals materials.<br>

Polymorphism of Bulk Boron Nitride

Boron nitride (BN) is a material with outstanding technological promise because of its exceptional thermochemical stability, structural, electronic and thermal conductivity properties, and extreme hardness. Yet, the relative thermodynamic stability of its most common polymorphs (diamond-like cubic and graphite-like hexagonal) has not been resolved satisfactorily because of the crucial role played by kinetic factors in the formation of BN phases at high temperatures and pressures (experiments), and by competing bonding, electrostatic and many-body dispersion forces in BN cohesion (theory). This lack of understanding hampers the development of potential technological applications, and challenges the boundaries of fundamental science. Here, we use high-level first-principles theories that correctly reproduce all important electronic interactions (the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation) to estimate with unprecedented accuracy the energy differences between BN polymorphs, and thus overcome the accuracy hurdle that hindered previous theoretical studies. We show that the ground-state phase of BN is cubic and that the frequently observed two-dimensional hexagonal polymorph becomes entropically stabilized over the cubic at temperatures slightly above ambient conditions (Tc = 63+-20'C). We also reveal a new low-symmetry monoclinic phase that is extremely competitive with the other low-energy polymorphs and which could explain the origins of the experimentally observed ``compressed h--BN'' phase. Our theoretical findings therefore should stimulate new experimental efforts in bulk BN as well as promote the use of high-level theories in modelling of technologically relevant van der Waals materials.<br>

Polymorphism of bulk boron nitride

Boron nitride (BN) is a material with outstanding technological promise due to its exceptional thermochemical stability, structural, electronic, and thermal conductivity properties, and extreme hardness. Yet, the relative thermodynamic stability of its most common polymorphs (diamond-like cubic and graphite-like hexagonal) has not been resolved satisfactorily because of the crucial role played by kinetic factors in the formation of BN phases at high temperatures and pressures (experiments) and by competing bonding and electrostatic and many-body dispersion forces in BN cohesion (theory). This lack of understanding hampers the development of potential technological applications and challenges the boundaries of fundamental science. Here, we use high-level first-principles theories that correctly reproduce all important electronic interactions (the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation) to estimate with unprecedented accuracy the energy differences between BN polymorphs and thus overcome the accuracy hurdle that hindered previous theoretical studies. We show that the ground-state phase of BN is cubic and that the frequently observed hexagonal polymorph becomes entropically stabilized over the cubic at temperatures slightly above ambient conditions (Tc→h = 335 ± 30 K). We also reveal a low-symmetry monoclinic phase that is extremely competitive with the other low-energy polymorphs and that could explain the origins of the experimentally observed “compressed h-BN” phase. Our theoretical findings therefore should stimulate new experimental efforts in bulk BN and promote the use of high-level theories in modeling of technologically relevant van der Waals materials.

Polymorphism of Bulk Boron Nitride

Boron nitride (BN) is a material with outstanding technological promise because of its exceptional thermochemical stability, structural, electronic and thermal conductivity properties, and extreme hardness. Yet, the relative thermodynamic stability of its most common polymorphs (diamond-like cubic and graphite-like hexagonal) has not been resolved satisfactorily because of the crucial role played by kinetic factors in the formation of BN phases at high temperatures and pressures (experiments), and by competing bonding, electrostatic and many-body dispersion forces in BN cohesion (theory). This lack of understanding hampers the development of potential technological applications, and challenges the boundaries of fundamental science. Here, we use high-level first-principles theories that correctly reproduce all important electronic interactions (the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation) to estimate with unprecedented accuracy the energy differences between BN polymorphs, and thus overcome the accuracy hurdle that hindered previous theoretical studies. We show that the ground-state phase of BN is cubic and that the frequently observed two-dimensional hexagonal polymorph becomes entropically stabilized over the cubic at temperatures slightly above ambient conditions (Tc = 63+-20'C). We also reveal a new low-symmetry monoclinic phase that is extremely competitive with the other low-energy polymorphs and which could explain the origins of the experimentally observed ``compressed h--BN'' phase. Our theoretical findings therefore should stimulate new experimental efforts in bulk BN as well as promote the use of high-level theories in modelling of technologically relevant van der Waals materials.<br>

Synergistic Combination Effect of Green Organic Derivatives on the Corrosion Inhibition of Mild steel in Simulated Seawater

Electrochemical studies of the synergistic combination of green organic derivatives, leucine and vanillin and the corrosion protection of mild steel in simulated seawater (3.5 wt.% NaCl) was done using potentiodynamic polarization, open circuit potential and morphological analysis. Results showed the combined admixture performed effectively with highest inhibition value of 89% at 3% volumetric content of the admixture. The performance of the compound was observed to be proportional to concentration with mixed type inhibition characteristics. Significant anodic shift of corrosion potential occurred due to film formation compared to the control solution at relative thermodynamic stability. The inhibition mechanism of the admixture occurred through physisorption reaction from thermodynamic calculations according to Langmuir, Frumkin and Freudlich isotherms with correlation coefficient above 0.7. Severe deterioration was observed on the morphology of mild steel with inhibitor compared to the steel from solution at highest inhibitor concentration.