Quantum Chemical calculations with HARLEM

Basic setup of a quantum chemical model of a molecular system in HARLEM is done in HaQCMod class. The class is derived from HaCompMod class and HaTextCmdTarget class, thus it has a basic functionality of a computational module and can accept text commands. Three dialog classes are directly associated with HaQCMod: QChemParDlg, LoadQCDatDlg, WaveFunAnalDlg. QChemParDlg manages setup of quantum chemical model, prepare input files and run external quantum chemical programs. LoadQCDatDlg dialog class manages load of the quantum chemical information such as molecular orbital coe.cients and energies obtained by the external program. WafeFunAnalDlg dialog class allows interactive graphical analysis of the quantum chemical data loaded in to the HaQC- Mod class such as display of molecular orbitals with isolevel 3D contours. HaQCMod specify gaussian basis set of the molecular system. Basis set information is handled by HaAtBasDB class. Several basis sets are stored inside the HaAtBasDB code, other basis set can be loaded from the files with basis set description in DALTON format stored in a specific directory of HARLEM installation. In addition to the regular gaussian basis set HaQCMod maintains active basis set which is a subset of the gaussian basis set of the system and currently can correspond to valence atomic orbitals ( setid option of the SetLocOrb function equal "VALENCE AO") or can coincide with a full basis set (setid equal "FULL BASIS" ). HaAtomOrbDB class handles setup of the basis of active orbitals. Currently expansion coe.cients of valence atomic orbitals for a particular gaussian basis set obtained from calculations on the isolated atoms are just specied in the code of the class HaAtomOrbDB. 122 There are several classes which calculate matricies of one-electronic operators such as matricies of electrical and magnetical dipole operators (classes HaOperR and HaOperRDelt correspondingly), operators of kinetic energy (HaOperKinEner class). All these operators are derived from the class HaOper1e (C++ abstruction for a general one-electronic operator) have the same member function calling interface and calculate the their matricies by the call to DENBAS function of the GAUSSIAN utility library, which is linked to the program. For the DENBAS function to work HaQCMod member functions LoadGauCom B and LoadGauCom IO fill GAUSSIAN common blocks specifing basis set of the system. We plan to substitute GAUSSIAN libraries by freeware gaussian integral package to remove copyright restrictions for the distribution of HARLEM. For a divide-and-conquer analysis HaQCMod member functions InsertLocOrbSubMat and ExtractLocOrbSubMat are especially important. These functions allow to manipulate ma- trix of any operator in the basis of active(valence) orbitals in terms of Atomic Group submatricies. Using these functions, for example, the matrix of the eective hamiltonian for the donor/acceptor electronic coupling calculations is divided into atomic group-group submatrices or assembled from group-group submatricies in divide-and-conquer calcula- tions. To perform calculations for optical response properties the most important classes are HaRPAvec(an abstraction for one electron pertubation of the Hartree-Fock ground state), HaRPAHam(an abstraction for RPA (Random Phase Approximation) for electronic Hamil- tonian ), HaRPAResolv(an abstraction for electronic Hamiltonian resolvent in the RPA approximation). HaRPAResolv class for any instance of HaRPAVec class specing RPA vector X calculate RPA vector jZi = (E jZi jZi routine from GAUSSIAN utility libraries linked to HARLEM (see appropriate equations in chapter 8. FORDIR perform appropriate convolutions of two-electron integrals with transition density of the RPA vector. Scalar product of Z with another RPA vector Y which is acomplished by a static function SProd of the HaRPAvec class Green Function matrix element between X and Y, which are related to optical observables as discussed in

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