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nuclear-electronic_orbital_method [2023/08/21 09:46] – [NEO examples] rmatalhasecknuclear-electronic_orbital_method [2024/01/29 13:45] (current) – removed explicit mention of NEO thresholds in a few examples rmata
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-====== Nuclear-electron orbital (NEO) method ======+====== Nuclear-electronic orbital (NEO) method ======
  
-The [[https://doi.org/10.1021/acs.chemrev.9b00798|Nuclear-electron orbital (NEO)]] method pioneered by Hammes-Schiffer and coworkers is available in **''Molpro''** for density fitted spin-restricted NEO-Hartree-Fock as well as a local-density fitting variant. It allows to handle a selected number of hydrogen nuclei as quantum particles by building a second Fock-matrix for the latter, coupling both subsystems (electrons and quantum protons) by a Coulomb operator. Further information about the method can be found in a  [[https://doi.org/10.21203/rs.3.rs-3231458/v1|preprint]].+The [[https://doi.org/10.1021/acs.chemrev.9b00798|Nuclear-electron orbital (NEO)]] method pioneered by Hammes-Schiffer and coworkers is available in **''Molpro''** for density fitted spin-restricted NEO-Hartree-Fock as well as a local-density fitting variant. It allows to handle a selected number of hydrogen nuclei as quantum particles by building a second Fock-matrix for the latter, coupling both subsystems (electrons and quantum protons) by a Coulomb operator. Further information about the method can be found [[https://doi.org/10.1021%2Facs.jctc.3c01055|here]].
  
   * **''DF-NEO-RHF'', //options//** calls the density-fitted NEO-Hartree-Fock program   * **''DF-NEO-RHF'', //options//** calls the density-fitted NEO-Hartree-Fock program
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   * **''NEORD'', //number//** sets the start for the fast rotational update of the orbitals in the local version   * **''NEORD'', //number//** sets the start for the fast rotational update of the orbitals in the local version
   * **''NOBLOCKDIAG''** disables the block diagonalization of the nuclear starting guess (this is generally not recommended!!)   * **''NOBLOCKDIAG''** disables the block diagonalization of the nuclear starting guess (this is generally not recommended!!)
 +  * **''NEOMIXBAS''** enables the use of user-defined mixed basis sets (see example for use)
 +===== Adaptive NEO =====
  
 +Optimization of quantum nuclei positions with the adaptive NEO approach, where the nuclear centroids are computed on-the-fly during the SCF iterations. This procedure is available by using the 
 +
 +<code>
 +ADAPTIVE
 +</code>
 +keyword in the NEO program input card.
 +
 +==== Threshold ====
 +
 +The thresholds for the convergence criteria of the nuclear centers during an adaptive NEO computation can be adjusted with the following keyword
 +
 +  * **''ADTHRES'', //number//** sets the convergence threshold for the nuclear centers in atomic units
 +  * **''ADITER'', //number//** sets the initial iteration for the start of the adaptive procedure (default=2)
 +==== Damping ====
 +
 +The shift of the nuclear basis function center towards the charge centroid can be damped with the following keyword
 +
 +  * **''ADDUMP'', //number//** sets the damping factor of the nuclear centroid shift
  
 ===== NEO examples ===== ===== NEO examples =====
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 </code> </code>
  
-The second example shows the input of a **''LDF-NEO-RHF''** computation of the same molecule starting from a prior RHF calculation. +The second example shows the input of a **''LDF-NEO-RHF''** computation of the same molecule starting from a prior RHF calculation. In this example a [[dump_density_or_orbital_values_cube|cube]] file is requested. This will output the quantum nuclei density.
  
 <code> <code>
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 </code> </code>
  
 +The following example shows a NEO calculation, where a user-defined mixed basis set is used. Thereby, the electronic basis set at the quantum nuclei is larger than for regular hydrogen atoms. The use of the **''NEOMIXBAS''** requires the additional definition of the **''elebas''** and **''elefit''** basis sets as shown below.
 +
 +<code>
 +memory,50,m
 +gdirect
 +nosym
 +
 +geometry={
 +3
 +
 +H1  -3.5008791    1.2736107    0.7596000
 +H2  -4.9109791    1.2967107    0.1521000
 +O   -3.9840791    1.3301107   -0.0574000
 +}
 +
 +charge=0
 +
 +basis={
 +default=cc-pvtz
 +H1=cc-pv5z
 +
 +set,nucbas
 +default=neo-basis
 +H1=pb4-f2
 +
 +set,nucfit
 +default=neo-basis
 +H1=10s10p10d10f
 +
 +set,elebas
 +default=cc-pvtz
 +H1=cc-pv5z
 +
 +set,elefit,context=jkfit
 +default=cc-pvtz
 +H1=cc-pv5z
 +}
 +
 +qnuc,H1
 +
 +{df-neo-rhf,maxdis=10,maxit=1000,df_basis=elefit
 +neoatden
 +neomixbas
 +}
 +</code>
 +
 +The example below shows the input for an adaptive NEO calculation, where the nuclear basis function centers convergence is set below 1E-5 bohr and a damping factor of 0.5 is applied.
 +
 +<code>
 +memory,50,m
 +gdirect
 +nosym
 +
 +geometry={
 +3
 +
 +H1  -3.5008791    1.2736107    0.7596000
 +H2  -4.9109791    1.2967107    0.1521000
 +O   -3.9840791    1.3301107   -0.0574000
 +}
 +
 +charge=0
 +
 +basis={
 +default=cc-pvdz
 +
 +set,nucbas
 +default=neo-basis
 +H1=pb4-f2
 +
 +set,nucfit
 +default=neo-basis
 +H1=10s10p10d10f
 +}
 +
 +qnuc,H1
 +
 +{df-neo-rhf,maxdis=10,maxit=500,df_basis=cc-pvdz
 +adaptive
 +adthres,1.d-5
 +addump,0.5
 +}
 +</code>
 ===== Bibliography ===== ===== Bibliography =====
  
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 ===(L)DF-NEO-RHF=== ===(L)DF-NEO-RHF===
  
-Lukas Hasecke, and Ricardo A. Mata [[https://doi.org/10.21203/rs.3.rs-3231458/v1|Nuclear quantum effects made accessible: local-density fitting in multicomponent methods]] //Research Square// **2023** preprint. +Lukas Hasecke, and Ricardo A. Mata [[https://doi.org/10.1021/acs.jctc.3c01055|Nuclear Quantum Effects Made Accessible: Local Density Fitting in Multicomponent Methods]] //J. Chem. Theory Comput.// **2023** //19// (22), 8223–8233.