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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Analytic calculations of higher-order molecular properties

Awarded: NOK 8.1 mill.

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In a previous project financed by the research council of Norway, which is now coming to an end, we have developed an open-ended (in terms of the order of the applied perturbations) response theory code, in which the atomic basis set may both be time and perturbation dependent. The formalism and code developed utilizes the density matrix in the atomic-orbital basis as the basic variable, enabling us to use linear-scaling technology to study higher-order properties of large molecules. In this project will in part extend the functionality of the code by extending it to the relativistic domain, using the response solver of the Dirac program to calculate higher-order molecular properties using perturbation-dependent basis set. This extension of the program t o the relativistic domain will lead to an increase in the possibilities for calculating molecular properties in the relativistic domain, including also various approximate Hamiltonians that will enable us to study in detail the effects of relativity. Our current implementation is limited by the availability of derivative two-electron (and to some extent also one-electron) integrals. Currently this restricts us to studying higher-order properties involving at most two geometry perturbations or two magneti c-field perturbations (and no mix of the two). In order to go beyond these limitations, we will develop open-ended one- and two-electron integral derivative programs. In order to explore the effects of electron correlation, we will also develop an open-e nded exchange-correlation kernel driver in the ALDA approximation, using automated code generation techniques. Correction terms arising from the geometry and magnetic field dependence of the basis set will be included. The goal of these developments is t he possibility of obtaining a better understanding of molecular properties of molecules containing elements from the entire periodic table, as well as facilitate the theoretical study of novel spectroscopies.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek