<p>This study introduces an orbital-free approach for the approximate evaluation of novel chemical structure descriptors, including the scalar projections of the partial exchange force onto the cumulative interelectron interaction and total static force densities, <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\([{\mathbf{F}}_{x}(\mathbf{r}) \cdot {\mathbf{F}}_{\text{ee}}(\mathbf{r})]/|{\mathbf{F}}_{\text{ee}}(\mathbf{r})|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">[</mo> <msub> <mi mathvariant="bold">F</mi> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>·</mo> <msub> <mi mathvariant="bold">F</mi> <mtext>ee</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">]</mo> </mrow> <mo stretchy="false">/</mo> <mrow> <mo stretchy="false">|</mo> <msub> <mi mathvariant="bold">F</mi> <mtext>ee</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\Phi }_{x}^{\text{em}}(\mathbf{r})=\left[{\mathbf{F}}_{x}(\mathbf{r})\cdot \mathcal{F}(\mathbf{r})\right]/|\mathcal{F}(\mathbf{r})|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="normal">Φ</mi> <mrow> <mi>x</mi> </mrow> <mtext>em</mtext> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mfenced close="]" open="["> <msub> <mi mathvariant="bold">F</mi> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>·</mo> <mi mathvariant="script">F</mi> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mfenced> <mo stretchy="false">/</mo> <mrow> <mo stretchy="false">|</mo> <mi mathvariant="script">F</mi> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, for which the electron density <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\rho (\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and the electrostatic potential <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({\varphi}_{\text{es}}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>φ</mi> <mtext>es</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> are leveraged. Specifically, the conservative&#xa0;exchange force&#xa0;field <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({\mathbf{F}}_{x}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi mathvariant="bold">F</mi> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, its divergence <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\({\nabla \cdot \mathbf{F}}_{x}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mrow> <mi mathvariant="normal">∇</mi> <mo>·</mo> <mi mathvariant="bold">F</mi> </mrow> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, and the stored potential energy density <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\frac{1}{2}{\left|{\mathbf{F}}_{x}(\mathbf{r})\right|}^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msup> <mrow> <mfenced close="|" open="|"> <msub> <mi mathvariant="bold">F</mi> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mfenced> </mrow> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> are expressed analytically in terms of <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\rho (\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and its derivatives, <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\nabla \rho (\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">∇</mi> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\({\nabla}^{2}\rho(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mrow> <mi mathvariant="normal">∇</mi> </mrow> <mn>2</mn> </msup> <mi>ρ</mi> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, employing the local density approximation. The applicability of this approach to experimentally derived <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\rho (\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ρ</mi> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\({\varphi }_{\text{es}}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>φ</mi> <mtext>es</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, reconstructed via multipole modeling, is demonstrated using the oxalic acid dihydrate crystal as a test case. The results confirm that the proposed methodology accurately reproduces key features of the descriptors, corroborated by comparisons with their Müller-framed counterparts. Certain limitations of the approximated functions are identified and discussed in detail. Importantly, these descriptors enable the quantification of the role of <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\({\mathbf{F}}_{x}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi mathvariant="bold">F</mi> <mi>x</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> in the mechanism of hydrogen bonding within supramolecular and crystal structures. Furthermore, the electrostatic-force and exchange-force scalar projections onto the total static force, <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\({\Phi}_{\text{es}}^{\text{em}}(\mathbf{r})=[{\mathbf{F}}_{\text{es}}(\mathbf{r})\cdot \mathcal{F}(\mathbf{r})]/|\mathcal{F}(\mathbf{r})|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="normal">Φ</mi> <mrow> <mtext>es</mtext> </mrow> <mtext>em</mtext> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mrow> <mo stretchy="false">[</mo> <msub> <mi mathvariant="bold">F</mi> <mtext>es</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>·</mo> <mi mathvariant="script">F</mi> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">]</mo> </mrow> <mo stretchy="false">/</mo> <mrow> <mo stretchy="false">|</mo> <mi mathvariant="script">F</mi> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\({\Phi }_{x}^{\text{em}}(\mathbf{r})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="normal">Φ</mi> <mrow> <mi>x</mi> </mrow> <mtext>em</mtext> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, are interpreted as the classical and nonclassical contributions, respectively, forming the total-static-force-field energy density, <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(\frac{1}{2}{[{\Phi}_{\text{es}}^{\text{em}}(\mathbf{r})+{\Phi }_{x}^{\text{em}}(\mathbf{r})]}^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msup> <mrow> <mo stretchy="false">[</mo> <msubsup> <mi mathvariant="normal">Φ</mi> <mrow> <mtext>es</mtext> </mrow> <mtext>em</mtext> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo>+</mo> <msubsup> <mi mathvariant="normal">Φ</mi> <mrow> <mi>x</mi> </mrow> <mtext>em</mtext> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="bold">r</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">]</mo> </mrow> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>.</p> Graphical Abstract <p></p>

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Functional roles of the electronic force fields in supramolecules and molecular crystals. Estimating the exchange-force component contributions from the inner-crystal electron density

  • Sergey V. Kartashov,
  • Robert R. Fayzullin

摘要

This study introduces an orbital-free approach for the approximate evaluation of novel chemical structure descriptors, including the scalar projections of the partial exchange force onto the cumulative interelectron interaction and total static force densities, \([{\mathbf{F}}_{x}(\mathbf{r}) \cdot {\mathbf{F}}_{\text{ee}}(\mathbf{r})]/|{\mathbf{F}}_{\text{ee}}(\mathbf{r})|\) [ F x ( r ) · F ee ( r ) ] / | F ee ( r ) | and \({\Phi }_{x}^{\text{em}}(\mathbf{r})=\left[{\mathbf{F}}_{x}(\mathbf{r})\cdot \mathcal{F}(\mathbf{r})\right]/|\mathcal{F}(\mathbf{r})|\) Φ x em ( r ) = F x ( r ) · F ( r ) / | F ( r ) | , for which the electron density \(\rho (\mathbf{r})\) ρ ( r ) and the electrostatic potential \({\varphi}_{\text{es}}(\mathbf{r})\) φ es ( r ) are leveraged. Specifically, the conservative exchange force field \({\mathbf{F}}_{x}(\mathbf{r})\) F x ( r ) , its divergence \({\nabla \cdot \mathbf{F}}_{x}(\mathbf{r})\) · F x ( r ) , and the stored potential energy density \(\frac{1}{2}{\left|{\mathbf{F}}_{x}(\mathbf{r})\right|}^{2}\) 1 2 F x ( r ) 2 are expressed analytically in terms of \(\rho (\mathbf{r})\) ρ ( r ) and its derivatives, \(\nabla \rho (\mathbf{r})\) ρ ( r ) and \({\nabla}^{2}\rho(\mathbf{r})\) 2 ρ ( r ) , employing the local density approximation. The applicability of this approach to experimentally derived \(\rho (\mathbf{r})\) ρ ( r ) and \({\varphi }_{\text{es}}(\mathbf{r})\) φ es ( r ) , reconstructed via multipole modeling, is demonstrated using the oxalic acid dihydrate crystal as a test case. The results confirm that the proposed methodology accurately reproduces key features of the descriptors, corroborated by comparisons with their Müller-framed counterparts. Certain limitations of the approximated functions are identified and discussed in detail. Importantly, these descriptors enable the quantification of the role of \({\mathbf{F}}_{x}(\mathbf{r})\) F x ( r ) in the mechanism of hydrogen bonding within supramolecular and crystal structures. Furthermore, the electrostatic-force and exchange-force scalar projections onto the total static force, \({\Phi}_{\text{es}}^{\text{em}}(\mathbf{r})=[{\mathbf{F}}_{\text{es}}(\mathbf{r})\cdot \mathcal{F}(\mathbf{r})]/|\mathcal{F}(\mathbf{r})|\) Φ es em ( r ) = [ F es ( r ) · F ( r ) ] / | F ( r ) | and \({\Phi }_{x}^{\text{em}}(\mathbf{r})\) Φ x em ( r ) , are interpreted as the classical and nonclassical contributions, respectively, forming the total-static-force-field energy density, \(\frac{1}{2}{[{\Phi}_{\text{es}}^{\text{em}}(\mathbf{r})+{\Phi }_{x}^{\text{em}}(\mathbf{r})]}^{2}\) 1 2 [ Φ es em ( r ) + Φ x em ( r ) ] 2 .

Graphical Abstract