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Structure, Bonding and Stability of Boron Substituted Tungsten Clusters

Akshata M. Waghmare, Sajeev S. Chacko, Balasaheb J. Nagare

TL;DR

This work addresses how boron substitution affects the structure, bonding, and stability of small tungsten clusters by employing density functional theory. Using B3LYP/QZVP calculations, it analyzes W$_n$B$_m$ clusters up to $n=5$, revealing that boron favors apex/edge sites, shortens W–B bonds, and forms B–B covalency at higher boron content, leading to more negative binding energies and reduced symmetry. Electronic structure shows a progressive localization of states on boron sites, increased HOMO–LUMO gaps, and higher chemical hardness, signaling enhanced electronic stability and lower reactivity. Vibrational spectra acquire characteristic W–B mid-frequency and B–B high-frequency bands, offering spectroscopic fingerprints of boron incorporation. Overall, boron substitution tunes both bonding and reactivity, guiding design principles for boron-rich tungsten materials at the nanoscale with potential bulk implications.

Abstract

In this study, we investigate effects of boron substitution on the structural and electronic properties of small tungsten clusters using density functional theory (DFT). We construct a series of tungsten boride clusters by replacing tungsten atoms with boron atoms to analyze their stability and other properties. Boron substitution in Wn clusters results in significant geometric distortions shortening the bond lengths and thereby reducing the clusters overall symmetry. The boron atoms prefers to occupy apex or edge positions. Its lower atomic radius and stronger electronegativity are the driving forces behind these structural changes.The binding energy per atom, HOMO LUMO gap, and chemical hardness increase with boron incorporation, indicating enhanced electronic stability.Additionally, negative chemical potentials are observed, which confirm greater charge localization and lower reactivity.BB stretches at high frequencies suggest strong boron-boron bonds with localized electrons, consistent with negative chemical potentials that promote charge retention over delocalization. WB modes in mid frequencies reflect metal boron interactions stabilizing the cluster, reducing overall reactivity as seen in prior Fukui analyses of electron density.Fukui functions pinpoint nucleophilic or electrophilic sites on W-B clusters, corroborating low reactivity from localized charges negative potentials confirm electrons are tightly bound, limiting site accessibility for reactions.

Structure, Bonding and Stability of Boron Substituted Tungsten Clusters

TL;DR

This work addresses how boron substitution affects the structure, bonding, and stability of small tungsten clusters by employing density functional theory. Using B3LYP/QZVP calculations, it analyzes WB clusters up to , revealing that boron favors apex/edge sites, shortens W–B bonds, and forms B–B covalency at higher boron content, leading to more negative binding energies and reduced symmetry. Electronic structure shows a progressive localization of states on boron sites, increased HOMO–LUMO gaps, and higher chemical hardness, signaling enhanced electronic stability and lower reactivity. Vibrational spectra acquire characteristic W–B mid-frequency and B–B high-frequency bands, offering spectroscopic fingerprints of boron incorporation. Overall, boron substitution tunes both bonding and reactivity, guiding design principles for boron-rich tungsten materials at the nanoscale with potential bulk implications.

Abstract

In this study, we investigate effects of boron substitution on the structural and electronic properties of small tungsten clusters using density functional theory (DFT). We construct a series of tungsten boride clusters by replacing tungsten atoms with boron atoms to analyze their stability and other properties. Boron substitution in Wn clusters results in significant geometric distortions shortening the bond lengths and thereby reducing the clusters overall symmetry. The boron atoms prefers to occupy apex or edge positions. Its lower atomic radius and stronger electronegativity are the driving forces behind these structural changes.The binding energy per atom, HOMO LUMO gap, and chemical hardness increase with boron incorporation, indicating enhanced electronic stability.Additionally, negative chemical potentials are observed, which confirm greater charge localization and lower reactivity.BB stretches at high frequencies suggest strong boron-boron bonds with localized electrons, consistent with negative chemical potentials that promote charge retention over delocalization. WB modes in mid frequencies reflect metal boron interactions stabilizing the cluster, reducing overall reactivity as seen in prior Fukui analyses of electron density.Fukui functions pinpoint nucleophilic or electrophilic sites on W-B clusters, corroborating low reactivity from localized charges negative potentials confirm electrons are tightly bound, limiting site accessibility for reactions.

Paper Structure

This paper contains 10 sections, 8 equations, 4 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Computational Details
  3. Results and Discussion
  4. Diatomic Molecules (W2, WB, B2)
  5. W_3-$n$B_$n$, ( $n$ = 0, 1, 2)
  6. W_4-$n$B_$n$, ( $n$ = 0, 1, 2)
  7. W_5-$n$B_$n$, ( $n$ = 0, 1, 2)
  8. Comparative Analysis of Structural and Electronic Trends Across W$_n$B$_m$ Series
  9. Conclusions
  10. acknowledgments

Figures (4)

  • Figure 1: Optimised geometries of WB clusters
  • Figure 2: Color-filled Electron density contour plots for W$_2$, WB, and B$_2$ dimers showing progressively changing bonding character from strong covalent (B$_2$) to covalent-metallic (W$_2$) with polar covalent behavior in W-B.
  • Figure 3: Vibrational spectra of W$_3$, W$_4$, and W$_5$ clusters with boron substitution.
  • Figure 4: Eigenvalue spectra of W$_3$, W$_4$, and W$_5$ clusters with boron substitution. Red and blue lines shows occupied and unoccupied orbitals respectively.