Many-body dispersion energy with fractionally ionic model for polarizability: Difference between revisions
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\frac{V^{\text{eff}}_p}{V^{\text{atom}}_p}</math>, | \frac{V^{\text{eff}}_p}{V^{\text{atom}}_p}</math>, | ||
whereby the volume ratios between interacting and non-interacting atoms (<math> \frac{V^{\text{eff}}_p}{V^{\text{atom}}_p} </math>) is obtained using conventional Hirshfeld partitioning{{hirshfeld:tca:1977}}. Although the MBD@rsSCS/FI employs a similar scaling relation: | whereby the volume ratios between interacting and non-interacting atoms (<math> \frac{V^{\text{eff}}_p}{V^{\text{atom}}_p} </math>) is obtained using conventional Hirshfeld partitioning{{cite|hirshfeld:tca:1977}}. Although the MBD@rsSCS/FI employs a similar scaling relation: | ||
:<math>\alpha_p^{\text{AIM}}(\omega) = \alpha_p^{\text{FI}}(\omega) | :<math>\alpha_p^{\text{AIM}}(\omega) = \alpha_p^{\text{FI}}(\omega) | ||
\frac{V^{\text{eff}}_p}{V^{\text{FI}}_p} </math>, | \frac{V^{\text{eff}}_p}{V^{\text{FI}}_p} </math>, | ||
it relies on Gould's model | it relies on Gould's model{{cite|gould:jctc:2016_a}} of frequency-dependent polarizabilities (<math> \alpha_p^{\text{FI}}(\omega) </math>) and charge densities of non-interacting fractional ions combined with iterative Hirshfeld partitioning{{cite|bultinck:jcp:07}}. Obviously, the MBD@rsSCS and the MBD@rsSCS/FI are equivalent for non-polar systems, such as graphite, but typically yield distinctly different results for polar and ionic materials{{cite|gould:jctc:2016_b}}. | ||
The MBD@rsSCS/FI method is invoked by setting {{TAG|IVDW}}=263. Optionally, the following parameters can be user-defined (the given values are the default ones): | The MBD@rsSCS/FI method is invoked by setting {{TAG|IVDW}}=263. Optionally, the following parameters can be user-defined (the given values are the default ones): | ||
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*{{TAG|LSCSGRAD}}=.TRUE. : compute gradients (or not) | *{{TAG|LSCSGRAD}}=.TRUE. : compute gradients (or not) | ||
*{{TAG|VDW_R0}} : radii for atomic reference (see also {{TAG|Tkatchenko-Scheffler method}}) | *{{TAG|VDW_R0}} : radii for atomic reference (see also {{TAG|Tkatchenko-Scheffler method}}) | ||
*{{TAG|ITIM}}=1: if set to +1, apply eigenvalue remapping to avoid unphysical cases where the eigenvalues of the matrix <math>\left(1-\mathbf{A}^{(0)}_{LR}(\omega) {\mathbf{T}}_{LR}({\mathbf{k}})\right) </math> are non-positive, see reference | *{{TAG|ITIM}}=1: if set to +1, apply eigenvalue remapping to avoid unphysical cases where the eigenvalues of the matrix <math>\left(1-\mathbf{A}^{(0)}_{LR}(\omega) {\mathbf{T}}_{LR}({\mathbf{k}})\right) </math> are non-positive, see reference{{cite|gould:jctc:2016_b}} for details | ||
{{NB|mind| | |||
{{NB|mind|This method requires the use of {{TAG|POTCAR}} files from the PAW dataset version 52 or later. | *This method requires the use of {{TAG|POTCAR}} files from the PAW dataset version 52 or later. | ||
*The parametrization of reference data is available only for elements of the first six rows of the periodic table except of the lanthanides. | |||
*The charge-density dependence of gradients is neglected. | |||
*This method is incompatible with the setting {{TAG|ADDGRID}}{{=}}''.TRUE.''. | |||
*It is essential that a sufficiently dense FFT grid (controlled via {{TAG|NGXF}}, {{TAG|NGYF}} and {{TAG|NGZF}} ) is used. We strongly recommend to use {{TAG|PREC}}{{=}}''Accurate'' for this type of calculations (in any case, avoid using {{TAG|PREC}}{{=}}''Low''}). | |||
*The method has sometimes numerical problems if highly polarizable atoms are located at short distances. In such a case the calculation terminates with an error message ''Error(vdw\_tsscs\_range\_separated\_k): d\_lr(pp)<{{=}}0''. Note that this problem is not caused by a bug, but rather it is due to a limitation of the underlying physical model. | |||
*Analytical gradients of the energy are implemented (fore details see reference {{cite|bucko:jpcm:16}}) and hence the atomic and lattice relaxations can be performed. | |||
*Due to the long-range nature of dispersion interactions, the convergence of energy with respect to the number of k-points should be carefully examined. | |||
*A default value for the free-parameter of this method is available only for the PBE ({{TAG|VDW_SR}}{{=}}0.83) and SCAN ({{TAG|VDW_SR}}{{=}}1.12) functionals. If any other functional is used, the value of {{TAG|VDW_SR}} must be specified in the {{TAG|INCAR}} file.}} | |||
== Related tags and articles == | == Related tags and articles == | ||
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[[Category:Exchange-correlation functionals]][[Category:van der Waals functionals]][[Category:Theory]] | [[Category:Exchange-correlation functionals]][[Category:van der Waals functionals]][[Category:Theory]] |
Latest revision as of 08:59, 20 October 2023
A variant of Many-body dispersion energy method based on fractionally ionic model for polarizability of Gould[1], hereafter dubbed MBD@rsSCS/FI, has been introduced in Ref.[2] Just like in the original MBD@rsSCS, dispersion energy in MBD@rsSCS/FI is computed using
- .
However, the two methods differ in the model used to approximate the atomic polarizabilities () needed to define tensor. The MBD@rsSCS makes use of the pre-computed static polarizabilities of neutral atoms ()
- ,
whereby the volume ratios between interacting and non-interacting atoms () is obtained using conventional Hirshfeld partitioning[3]. Although the MBD@rsSCS/FI employs a similar scaling relation:
- ,
it relies on Gould's model[1] of frequency-dependent polarizabilities () and charge densities of non-interacting fractional ions combined with iterative Hirshfeld partitioning[4]. Obviously, the MBD@rsSCS and the MBD@rsSCS/FI are equivalent for non-polar systems, such as graphite, but typically yield distinctly different results for polar and ionic materials[2].
The MBD@rsSCS/FI method is invoked by setting IVDW=263. Optionally, the following parameters can be user-defined (the given values are the default ones):
- VDW_SR=0.83 : scaling parameter
- LVDWEXPANSION=.FALSE. : writes the two- to six- body contributions to the MBD dispersion energy in the OUTCAR (LVDWEXPANSION=.TRUE.)
- LSCSGRAD=.TRUE. : compute gradients (or not)
- VDW_R0 : radii for atomic reference (see also Tkatchenko-Scheffler method)
- ITIM=1: if set to +1, apply eigenvalue remapping to avoid unphysical cases where the eigenvalues of the matrix are non-positive, see reference[2] for details
Mind:
|
Related tags and articles
VDW_ALPHA, VDW_C6, VDW_R0, VDW_SR, LVDWEXPANSION, LSCSGRAD, IVDW, Tkatchenko-Scheffler method, Self-consistent screening in Tkatchenko-Scheffler method, Tkatchenko-Scheffler method with iterative Hirshfeld partitioning, Many-body dispersion energy
References
- ↑ a b T. Gould and T. Bučko, C6 Coefficients and Dipole Polarizabilities for All Atoms and Many Ions in Rows 1–6 of the Periodic Table, J. Chem. Theory Comput. 12, 3603 (2016).
- ↑ a b c T. Gould, S. Lebègue, J. G. Ángyán, and T. Bučko, A Fractionally Ionic Approach to Polarizability and van der Waals Many-Body Dispersion Calculations, J. Chem. Theory Comput. 12, 5920 (2016).
- ↑ F. Hirshfeld, Bonded-atom fragments for describing molecular charge densities, Theor. Chim. Acta 44, 129 (1977).
- ↑ P. Bultinck, C. Van Alsenoy, P. W. Ayers, and R. Carbó Dorca, J. Chem. Phys. 126, 144111 (2007).
- ↑ T. Bučko, S. Lebègue, T. Gould, and J. G. Ángyán, J. Phys.: Condens. Matter 28, 045201 (2016).