Many-body enhancement of positron annihilation in metals: the choice of electron density parameter rs

The effective electron density for positron annihilation in substituted aliphatic and aromatic liquid compounds has been determined. For the aliphatic hydrocarbons the molecular electron density Ne increases linearly with an increase in chain length and is equal to the sum of the partial electron densities of the substituent methyl (Ne(CH3) = 1.18) and methylene (Ne(CH2) = 1.28) groups.The values are approximately 10% lower for aromatic systems. The partial electron densities of substituted halogen atoms increase with atomic number and are: fluorine (9.3), chlorine (10.0), bromine (14.4) and iodine (23.0). For the aliphatic alcohols the partial Ne(OH) value decreases from 1.35 in methanol to 0.86 in octanol.

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Quasi-particle Contribution in Thermal Expansion and Thermal Conductivity in Metals

Materials Science Materials Review ◽

10.18063/msmr.v2i2.343 ◽

2018 ◽

Vol 2 (2) ◽

Author(s):

O. G. Edema1 ◽

O. M. Osiele2 ◽

S. I. Otobo1 ◽

A. O. Akinbolusere1

Keyword(s):

Thermal Conductivity ◽

Thermal Expansion ◽

Electron Density ◽

Materials Science ◽

Landau Theory ◽

Density Parameter ◽

Density Region ◽

Heavy Particles ◽

Bulk Properties ◽

Potential Applications

In this paper the modified Landau theory of Fermi Liquids was used to compute the thermal expansion and thermal conductivity of quasi-particles in metals. The result revealed that as temperature increases the thermal expansion of quasi-particles in metals increases in all the metals investigated. It is also observed that as the electron density parameter increases the thermal expansion of quasi-particles increases. This shows that at low density region the thermal expansion of quasi-particles is large. The result obtained for the thermal conductivity of quasi-particles in metals revealed that for all the metals computed the thermal conductivity of quasi-particles decreases as temperature increases. This seems to suggest that as temperature increases the separation between quasi-particles increases because they are not heavy particles hence, the rate of absorbing heat decreases. The computed thermal expansion and thermal conductivity of quasi-particles are in better agreement with experimental values. This suggests that the introduction of the electron density parameter is promising in predicting the contribution of quasi-particles to the bulk properties of metals. This study revealed the extent to which quasi-particles contribute to the bulk properties of metals, which assisted their potential applications in materials science and engineering development.

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Resonance-Assisted Hydrogen Bond—Revisiting the Original Concept in the Context of Its Criticism in the Literature

International Journal of Molecular Sciences ◽

10.3390/ijms23010233 ◽

2021 ◽

Vol 23 (1) ◽

pp. 233

Author(s):

Małgorzata Domagała ◽

Sílvia Simon and Marcin Palusiak

Keyword(s):

Hydrogen Bond ◽

Interaction Energy ◽

Electron Density ◽

Intermolecular Hydrogen Bond ◽

Many Body ◽

Body Interaction ◽

The Many ◽

Three Body ◽

Interaction Approach ◽

Original Concept

In the presented research, we address the original concept of resonance-assisted hydrogen bonding (RAHB) by means of the many-body interaction approach and electron density delocalization analysis. The investigated molecular patterns of RAHBs are open chains consisting of two to six molecules in which the intermolecular hydrogen bond stabilizes the complex. Non-RAHB counterparts are considered to be reference systems. The results show the influence of the neighbour monomers on the unsaturated chains in terms of the many-body interaction energy contribution. Exploring the relation between the energy parameters and the growing number of molecules in the chain, we give an explicit extrapolation of the interaction energy and its components in the infinite chain. Electron delocalization within chain motifs has been analysed from three different points of view: three-body delocalization between C=C-C, two-body hydrogen bond delocalization indices and also between fragments (monomers). A many-body contribution to the interaction energy as well as electron density helps to establish the assistance of resonance in the strength of hydrogen bonds upon the formation of the present molecular chains. The direct relation between interaction energy and delocalization supports the original concept, and refutes some of the criticisms of the RAHB idea.

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