scholarly journals Static and lattice vibrational energy differences between polymorphs

CrystEngComm ◽  
2015 ◽  
Vol 17 (28) ◽  
pp. 5154-5165 ◽  
Author(s):  
Jonas Nyman ◽  
Graeme M. Day
Keyword(s):  
Free Energy ◽  
Vibrational Energy ◽  
Lattice Energy ◽  
Energy Entropy

Lattice energy, entropy and free energy differences for over 500 pairs of known polymorphs are computed and discussed.

scholarly journals DFT Investigation of Hydrogen Atom Abstraction from NHC-Boranes by Methyl, Ethyl and Cyanomethyl Radicals—Composition and Correlation Analysis of Kinetic Barriers

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4509
Author(s):  
Hong-jie Qu ◽  
Lang Yuan ◽  
Cai-xin Jia ◽  
Hai-tao Yu ◽  
Hui Xu
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Vibrational Energy ◽  
Hydrogen Atom Abstraction ◽  
Reaction Energy ◽  
Energy Barriers ◽  
Energy Correction ◽  
Kinetic Barriers

Understanding the hydrogen atom abstraction (HAA) reactions of N-heterocyclic carbene (NHC)-boranes is essential for extending the practical applications of boron chemistry. In this study, density functional theory (DFT) computations were performed for the HAA reactions of a series of NHC-boranes attacked by •CH2CN, Me• and Et• radicals. Using the computed data, we investigated the correlations of the activation and free energy barriers with their components, including the intrinsic barrier, the thermal contribution of the thermodynamic reaction energy to the kinetic barriers, the activation Gibbs free energy correction and the activation zero-point vibrational energy correction. Furthermore, to describe the dependence of the activation and free energy barriers on the thermodynamic reaction energy or reaction Gibbs free energy, we used a three-variable linear model, which was demonstrated to be more precise than the two-variable Evans–Polanyi linear free energy model and more succinct than the three-variable Marcus-theory-based nonlinear HAA model. The present work provides not only a more thorough understanding of the compositions of the barriers to the HAA reactions of NHC-boranes and the HAA reactivities of the substrates but also fresh insights into the suitability of various models for describing the relationships between the kinetic and thermodynamic physical quantities.

Free energy and lattice energy in real ionic crystals

1969 ◽  
Vol 9 (2) ◽  
pp. 102-103
Author(s):  
A. A. Vorob'ev
Keyword(s):  
Free Energy ◽  
Lattice Energy ◽  
Ionic Crystals

scholarly journals HIGH-TEMPERATURE FREE ENERGY, ENTROPY, ENTHALPY AND HEAT CAPACITY OF THORIUM SULFATE1

1960 ◽  
Vol 64 (7) ◽  
pp. 911-914 ◽  
Author(s):  
S. W. Mayer ◽  
B. B. Owens ◽  
T. H. Rutherford ◽  
R. B. Serrins
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
High Temperature ◽  
Energy Entropy

scholarly journals Intrinsic Flexibility of the EMT Zeolite Framework Under Pressure

2019 ◽  
Author(s):  
Antony Nearchou ◽  
Mero-Lee U. Cornelius ◽  
Jonathan M. Skelton ◽  
Zoe Jones ◽  
Andrew Cairns ◽  
...  
Keyword(s):  
Free Energy ◽  
Computational Modelling ◽  
Lattice Energy ◽  
Vibrational Entropy ◽  
Organic Additives ◽  
X Ray Diffraction ◽  
Zeolite Framework ◽  
Guest Molecules ◽  
Fau Zeolite

<p>The roles of organic additives in the assembly and crystallisation of zeolites is still not fully understood. This is important when attempting to prepare novel frameworks to produce new zeolites. We consider 18-crown-6 ether as an additive, which has previously been shown to differentiate between the EMT and FAU zeolite frameworks. However, it is unclear whether this distinction is dictated by influences on the metastable free-energy landscape or geometric templating. Using high pressure synchrotron X-ray diffraction, we have observed that the presence of 18C6 does not impact the EMT framework flexibility – agreeing with our previous geometric simulations and suggesting that 18C6 does not behave as a true geometric template. This was further studied with computational modelling, using first-principles comparative periodic DFT and lattice-dynamics calculations. It is shown that the lattice energy of FAU is more stable than EMT, however this is strongly impacted by the presence of solvent/guest molecules in the framework. Furthermore, the EMT topology possesses a greater vibrational entropy, being stabilised by free energy at finite temperature. Overall, these findings demonstrate that the role of the 18C6 additive is to influence the free-energy of crystallisation to assemble the EMT framework as opposed to FAU. </p>

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