howto:gfn1xtb
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- | ====== How to run a GFN1-xTB calculation ====== | + | This page has been moved to: https://manual.cp2k.org/trunk/methods/semiempiricals/xtb.html |
- | + | ||
- | This is a short tutorial on how to run GFN1-XTB computations. The details on the theory and the original implementation by Grimme can be found in [[https://pubs.acs.org/doi/full/10.1021/acs.jctc.7b00118]]. | + | |
- | Please cite this paper if you were to use the GFN1-XTB module. | + | |
- | + | ||
- | ===== Brief theory recap ===== | + | |
- | + | ||
- | The semi-empirical GFN1-xTB energy expression comprises contributions due to electronic (el), atom-pairwise repulsion (rep), dispersion (disp), and halogen-bonding (XB) terms, | + | |
- | + | ||
- | \begin{equation}\label{gfnxtb1_energy_expression} | + | |
- | \begin{aligned} | + | |
- | E_{\rm{\tiny{GFN1-xTB}}} = E_{\rm{\tiny{EL}}} + E_{\rm{\tiny{REP}}} + E_{\rm{\tiny{DISP}}} + E_{\rm{\tiny{XB}}} + E_{\rm{\tiny{NONBOND}}}\, | + | |
- | \end{aligned} | + | |
- | \end{equation} | + | |
- | + | ||
- | 1. The electronic energy contribution, | + | |
- | + | ||
- | \begin{equation}\label{electronic_energy} | + | |
- | \begin{aligned} | + | |
- | E_{\rm{\tiny{el}}} = \sum_i^{\rm{\tiny{occ}}} n_i \langle \Psi_i | h_0 | \Psi_i \rangle + \frac{1}{2} \sum_{A,B} \sum_{{l}^A}\sum_{{l' | + | |
- | \end{aligned} | + | |
- | \end{equation} | + | |
- | + | ||
- | contains zeroth-order contributions based on a zeroth-order Hamiltonian $h_0$, the valence molecular orbitals $\Psi_i$, occupation numbers $n_i$ as well as second-order contributions which are optimized self-consistently as well as third-order diagonal contributions. | + | |
- | The second order contributions are described using the semi-empirical electron repulsion operator $\gamma_{AB, | + | |
- | + | ||
- | \begin{equation}\label{scc_charges} | + | |
- | \begin{aligned} | + | |
- | p_l^A = p_l^{A_0} - \sum_{\nu}^{N_{\rm{\tiny{AO}}}} \sum_{\mu \in A, \mu \in l} S_{\mu \nu } P_{\mu \nu} \, , | + | |
- | \end{aligned} | + | |
- | \end{equation} | + | |
- | + | ||
- | referring to the atomic orbital overlap matrix $\mathbf{S}$ and the density matrix $\mathbf{P}$. | + | |
- | + | ||
- | The remaining diagonal terms represent a cubic charge correction based on the Mulliken charge $q_A$ of atom $A$ and the charge derivative $\Gamma_A$ of the atomic Hubbard parameter $\eta_A$. | + | |
- | Furthermore, | + | |
- | + | ||
- | 2. Repulsion is described via an atom-pairwise potential, | + | |
- | + | ||
- | \begin{equation}\label{repulsion} | + | |
- | \begin{aligned} | + | |
- | E_{\rm{\tiny{rep}}} = \sum_{AB} \frac{Z_A^{\rm{\tiny{eff}}} Z_B^{\rm{\tiny{eff}}} }{R_{AB}} \exp^{- (\alpha_A \alpha_B)^{1/ | + | |
- | \end{aligned} | + | |
- | \end{equation} | + | |
- | with the effective nuclear charge $\mathbf{Z}^{\rm{\tiny{eff}}}$ as well as the global or element-specific parameters $k_f$ and $\alpha$. | + | |
- | + | ||
- | 3. Dispersion is included by the well-established D3 method in the BJ-damping scheme[[https:// | + | |
- | + | ||
- | 4. Corrections for element-specific interactions are possible using either a halogen-bonding correction term (XB) or a generic nonbonding potential correction (NONBOND). Note that the generic nonbonding potential correction is CP2K specific. | + | |
- | + | ||
- | + | ||
- | ===== The GFN1-xTB input section ===== | + | |
- | + | ||
- | The most important keywords and subsections of section '' | + | |
- | * '' | + | |
- | * '' | + | |
- | * '' | + | |
- | * '' | + | |
- | + | ||
- | The additional keywords '' | + | |
- | + | ||
- | + | ||
- | ===== Simple examples ===== | + | |
- | + | ||
- | ==== GFN1-xTB ground-state energy for ==== | + | |
- | + | ||
- | + | ||
- | ==== Adding a generic correction potential ==== | + |
howto/gfn1xtb.1658226486.txt.gz · Last modified: 2022/07/19 10:28 by ahehn