DFT-ulg: Difference between revisions
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where the first two summations are over all <math>N_{at}</math> atoms in the unit cell and the third summation is over all translations of the unit cell <math>{\mathbf{L}}=(l_1,l_2,l_3)</math> where the prime indicates that <math>i\not=j</math> for <math>{\mathbf{L}}=0</math>. <math>C_{6ij}</math> denotes the dispersion coefficient for the atom pair <math>ij</math>, <math>{r}_{ij,\mathbf{L}}</math> is the distance between atom <math>i</math> located in the reference cell <math>\mathbf{L}=0</math> and atom <math>j</math> in the cell <math>L</math>. | where the first two summations are over all <math>N_{at}</math> atoms in the unit cell and the third summation is over all translations of the unit cell <math>{\mathbf{L}}=(l_1,l_2,l_3)</math> where the prime indicates that <math>i\not=j</math> for <math>{\mathbf{L}}=0</math>. <math>C_{6ij}</math> denotes the dispersion coefficient for the atom pair <math>ij</math>, <math>{r}_{ij,\mathbf{L}}</math> is the distance between atom <math>i</math> located in the reference cell <math>\mathbf{L}=0</math> and atom <math>j</math> in the cell <math>L</math>. | ||
== Usage == | |||
The DFT-ulg method can be activated by setting {{TAG|IVDW}}=''3''. The parameters in the DFT-ulg method (see Ref. {{cite|kim:jpcl:2012}} for details) that can be modified are listed below. | |||
*{{TAG|VDW_RADIUS}}=50.0 : cutoff radius (in <math>\AA</math>) for pair interactions | *{{TAG|VDW_RADIUS}}=50.0 : cutoff radius (in <math>\AA</math>) for pair interactions | ||
*{{TAG|VDW_S6}}=0.7012 : global scaling parameter <math>s_{lg}</math> | *{{TAG|VDW_S6}}=0.7012 : global scaling parameter <math>s_{lg}</math> | ||
*{{TAG|VDW_D}}=0.6966 : universal correction parameter <math>b_{lg}</math> | *{{TAG|VDW_D}}=0.6966 : universal correction parameter <math>b_{lg}</math> | ||
*{{TAG|VDW_C6}}=[real array] : <math>C_6</math> parameters (<math>\mathrm{Jnm}^{6}\mathrm{mol}^{-1}</math>) for each species defined in the {{TAG|POSCAR}} file | *{{TAG|VDW_C6}}=[real array] : <math>C_6</math> parameters (<math>\mathrm{Jnm}^{6}\mathrm{mol}^{-1}</math>) for each species defined in the {{TAG|POSCAR}} file | ||
*{{TAG|VDW_R0}}=[real array] : <math>R_0</math> parameters (<math>\AA</math>) for each species defined in the {{TAG|POSCAR}} file | *{{TAG|VDW_R0}}=[real array] : <math>R_0</math> parameters (<math>\AA</math>) for each species defined in the {{TAG|POSCAR}} file | ||
*{{TAG|LVDW_EWALD}}=''.FALSE.'' : the lattice summation in <math>E_{\mathrm{disp}}</math> expression is computed by means of Ewald's summation (''.TRUE.'' ) or via a real space summation over all atomic pairs within cutoff radius {{TAG|VDW_RADIUS}} (''.FALSE.''). (available in VASP.5.3.5 and later) | *{{TAG|LVDW_EWALD}}=''.FALSE.'' : the lattice summation in <math>E_{\mathrm{disp}}</math> expression is computed by means of Ewald's summation (''.TRUE.'' ) or via a real space summation over all atomic pairs within cutoff radius {{TAG|VDW_RADIUS}} (''.FALSE.''). (available in VASP.5.3.5 and later) | ||
{{NB|mind|The default value of the parameter <math>s_{lg}</math> (0.7012) was determined in conjunction with the PBE {{TAG|GGA}} functional{{cite|kim:jpcl:2012}}. Therefore, it is not recommended to use the DFT-ulg dispersion correction with a {{TAG|GGA}} functional other than PBE, unless <math>s_{lg}</math> is reoptimized.}} | |||
== Related tags and articles == | == Related tags and articles == | ||
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{{TAG|VDW_R0}}, | {{TAG|VDW_R0}}, | ||
{{TAG|LVDW_EWALD}}, | {{TAG|LVDW_EWALD}}, | ||
{{TAG|IVDW}} | {{TAG|IVDW}}, | ||
{{TAG|DFT-D2}} | |||
== References == | == References == | ||
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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]][[Category:Howto]] | ||
Latest revision as of 14:42, 6 March 2025
In the DFT-ulg method of Kim et al.[1], the correction term takes the form:
- [math]\displaystyle{ E_{\mathrm{disp}} = -\frac{1}{2} s_{lg}\sum_{i=1}^{N_{at}} \sum_{j=1}^{N_{at}} \sum_{\mathbf{L}} {}^{\prime} \frac{C_{6ij}}{r_{ij,L}^{6}+b_{lg}(R_{0}^{ij})^{6}} }[/math]
where the first two summations are over all [math]\displaystyle{ N_{at} }[/math] atoms in the unit cell and the third summation is over all translations of the unit cell [math]\displaystyle{ {\mathbf{L}}=(l_1,l_2,l_3) }[/math] where the prime indicates that [math]\displaystyle{ i\not=j }[/math] for [math]\displaystyle{ {\mathbf{L}}=0 }[/math]. [math]\displaystyle{ C_{6ij} }[/math] denotes the dispersion coefficient for the atom pair [math]\displaystyle{ ij }[/math], [math]\displaystyle{ {r}_{ij,\mathbf{L}} }[/math] is the distance between atom [math]\displaystyle{ i }[/math] located in the reference cell [math]\displaystyle{ \mathbf{L}=0 }[/math] and atom [math]\displaystyle{ j }[/math] in the cell [math]\displaystyle{ L }[/math].
Usage
The DFT-ulg method can be activated by setting IVDW=3. The parameters in the DFT-ulg method (see Ref. [1] for details) that can be modified are listed below.
- VDW_RADIUS=50.0 : cutoff radius (in [math]\displaystyle{ \AA }[/math]) for pair interactions
- VDW_S6=0.7012 : global scaling parameter [math]\displaystyle{ s_{lg} }[/math]
- VDW_D=0.6966 : universal correction parameter [math]\displaystyle{ b_{lg} }[/math]
- VDW_C6=[real array] : [math]\displaystyle{ C_6 }[/math] parameters ([math]\displaystyle{ \mathrm{Jnm}^{6}\mathrm{mol}^{-1} }[/math]) for each species defined in the POSCAR file
- VDW_R0=[real array] : [math]\displaystyle{ R_0 }[/math] parameters ([math]\displaystyle{ \AA }[/math]) for each species defined in the POSCAR file
- LVDW_EWALD=.FALSE. : the lattice summation in [math]\displaystyle{ E_{\mathrm{disp}} }[/math] expression is computed by means of Ewald's summation (.TRUE. ) or via a real space summation over all atomic pairs within cutoff radius VDW_RADIUS (.FALSE.). (available in VASP.5.3.5 and later)
| Mind: The default value of the parameter [math]\displaystyle{ s_{lg} }[/math] (0.7012) was determined in conjunction with the PBE GGA functional[1]. Therefore, it is not recommended to use the DFT-ulg dispersion correction with a GGA functional other than PBE, unless [math]\displaystyle{ s_{lg} }[/math] is reoptimized. |
Related tags and articles
VDW_RADIUS, VDW_S6, VDW_D, VDW_C6, VDW_R0, LVDW_EWALD, IVDW, DFT-D2