- Timestamp:
- May 18, 2016, 10:02:53 PM (9 years ago)
- Branches:
- Action_Thermostats, Add_AtomRandomPerturbation, Add_FitFragmentPartialChargesAction, Add_RotateAroundBondAction, Add_SelectAtomByNameAction, Added_ParseSaveFragmentResults, Adding_Graph_to_ChangeBondActions, Adding_MD_integration_tests, Adding_ParticleName_to_Atom, Adding_StructOpt_integration_tests, Automaking_mpqc_open, AutomationFragmentation_failures, Candidate_v1.5.4, Candidate_v1.6.0, Candidate_v1.6.1, ChangeBugEmailaddress, ChangingTestPorts, ChemicalSpaceEvaluator, CombiningParticlePotentialParsing, Combining_Subpackages, Debian_Package_split, Debian_package_split_molecuildergui_only, Disabling_MemDebug, Docu_Python_wait, EmpiricalPotential_contain_HomologyGraph, EmpiricalPotential_contain_HomologyGraph_documentation, Enable_parallel_make_install, Enhance_userguide, Enhanced_StructuralOptimization, Enhanced_StructuralOptimization_continued, Example_ManyWaysToTranslateAtom, Exclude_Hydrogens_annealWithBondGraph, FitPartialCharges_GlobalError, Fix_ChargeSampling_PBC, Fix_ChronosMutex, Fix_FitPartialCharges, Fix_FitPotential_needs_atomicnumbers, Fix_ForceAnnealing, Fix_IndependentFragmentGrids, Fix_ParseParticles, Fix_ParseParticles_split_forward_backward_Actions, Fix_PopActions, Fix_QtFragmentList_sorted_selection, Fix_Restrictedkeyset_FragmentMolecule, Fix_StatusMsg, Fix_StepWorldTime_single_argument, Fix_Verbose_Codepatterns, Fix_fitting_potentials, Fixes, ForceAnnealing_goodresults, ForceAnnealing_oldresults, ForceAnnealing_tocheck, ForceAnnealing_with_BondGraph, ForceAnnealing_with_BondGraph_continued, ForceAnnealing_with_BondGraph_continued_betteresults, ForceAnnealing_with_BondGraph_contraction-expansion, FragmentMolecule_checks_bonddegrees, GeometryObjects, Gui_Fixes, Gui_displays_atomic_force_velocity, IndependentFragmentGrids, IndependentFragmentGrids_IndividualZeroInstances, IndependentFragmentGrids_IntegrationTest, IndependentFragmentGrids_Sole_NN_Calculation, JobMarket_RobustOnKillsSegFaults, JobMarket_StableWorkerPool, JobMarket_unresolvable_hostname_fix, ODR_violation_mpqc_open, PartialCharges_OrthogonalSummation, PdbParser_setsAtomName, PythonUI_with_named_parameters, QtGui_reactivate_TimeChanged_changes, Recreated_GuiChecks, Rewrite_FitPartialCharges, RotateToPrincipalAxisSystem_UndoRedo, SaturateAtoms_findBestMatching, SaturateAtoms_singleDegree, StoppableMakroAction, Subpackage_CodePatterns, Subpackage_JobMarket, Subpackage_LinearAlgebra, Subpackage_levmar, Subpackage_mpqc_open, Subpackage_vmg, Switchable_LogView, ThirdParty_MPQC_rebuilt_buildsystem, TrajectoryDependenant_MaxOrder, TremoloParser_IncreasedPrecision, TremoloParser_MultipleTimesteps, TremoloParser_setsAtomName, Ubuntu_1604_changes, stable
- Children:
- 01120c
- Parents:
- d9dbef
- git-author:
- Frederik Heber <heber@…> (03/07/16 13:51:28)
- git-committer:
- Frederik Heber <heber@…> (05/18/16 22:02:53)
- File:
-
- 1 edited
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doc/userguide/userguide.xml
rd9dbef rd8ed62 1845 1845 behavior in the molecular fragment, namely the (covalently) bonded interaction. 1846 1846 In order to model the Coulomb long-range interaction as well without solving 1847 for the electronic ground state in each time step, parti clecharges1847 for the electronic ground state in each time step, partial charges 1848 1848 are used that capture to some degree the created dipoles due to 1849 charge transfer from one atom to another when bonded.</para> 1850 <para>Note that so far the placement of partial charges is restricted to the position of nuclei in the molecular system. There are more complex ways of placing partial charges, e.g. as employed in higher TIP water molecules, that also use anti-bonding potentials. This is so far not implemented.</para> 1849 charge transfer from one atom to another when bonded. These are called 1850 partial charges because they combine both nuclei and electronic 1851 charges to yield an in general fractional charge.</para> 1852 <para>Note that so far the placement of partial charges is restricted 1853 to the position of nuclei in the molecular system. There are more 1854 complex ways of placing partial charges, e.g. as employed in higher 1855 TIP water molecules, that also use anti-bonding potentials. This is 1856 so far not implemented.</para> 1851 1857 <para>To allow least-squares regression of these partial charges, we 1852 1858 need the results of long-range calculations and the <emphasis role="bold">store-grids</emphasis> 1853 option (see above under <link linkend="fragmentation">Fragmentation </link>) must have been given. With these sampled charge density and 1854 Coulomb potential stored in the homology containers, we call this 1855 action as follows.</para> 1859 option (see above under <link linkend="fragmentation">Fragmentation </link>) 1860 must have been given.</para> 1861 <para>Furthermore, we require associations between selected atoms and 1862 the fragments, residing in the <link linkend="homology">Homology container</link>. 1863 These are contained in the <link linkend="atomfragments">AtomFragments association</link> 1864 container, that can also be parsed and stored.</para> 1865 <para>With these sampled charge density and Coulomb potential stored 1866 in the homology containers, we call this action as follows.</para> 1856 1867 <programlisting> 1857 1868 ... --fit-partial-charges \ 1858 --fragment-charges 8 1 1 \ 1859 --potential-file water.potentials \ 1860 --radius 0.2 1861 </programlisting> 1862 <para>This will again use a water molecule as homologous fragment 1863 "key" to request all configurations of this type from the homologies container. Results are 1864 stored in <filename>water.potentials</filename>. The radius is used 1865 to mark the region directly around the nuclei from the fit 1866 procedure. As here the charges of the core electrons and the nuclei 1867 itself dominate, we however are only interested in a good 1869 --potential-file water.particles \ 1870 --radius 1.5 1871 </programlisting> 1872 <para>Assume that a water molecule has been selected previously. Then 1873 all homologous fragments that contain any of the water molecules are 1874 used as "key" to request all configurations of this type 1875 from the homologies container. For each of the atoms then an average 1876 partial charge is computed by fitting their respective Coulomb 1877 potential to the obtained from the fragment calculations. Resulting 1878 values are stored in <filename>water.particles</filename>. The 1879 radius is used to mask a certain region directly around the nuclei 1880 from the fit procedure. As here the charges of the core electrons and 1881 the nuclei itself dominate, we however are only interested in a good 1868 1882 approximation to the long-range potential, this mask radius allows 1869 1883 to give the range of the excluded zone.</para>
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