Development of Relativistic Configuration Interaction Method using Reduced Frozen-core Approximation

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(1) Relativistic frozen-core approximation (RFCA)-After considerable amount of numerical experiments we have now found the best method for determining the corelike basis sets ; First we perform a Dirac-Fock-Rooth aan calculation using a large number of basis functions. Then we fit the valence orbital using smaller number of basis functions. We have tried various kinds of spectral representations for the core Hamiltonian matrix. However, the obtained numerical values are not accurate enough to reproduce their exact values and further works remain to be done.(2) Relativistic con figuration-in teraction (CI) program-We had many difficulties when formulating efficient algorithm for treatment of 4-component wave functions and of huge number of molecular integrals. We have now a small CI program which should, however, be improved further.(3) All-electron molecular calculations-By their in terests and for the references for the RFCA, we performed relativistic and non relativistic SCF calculations on GdF, GdF_2, and ThO and estimated the relativistic effects in these molecules.(4) Methods for calculation of molecular integrals-We found reccurence formulas for the molecular integrals over Laguerre Gaussian-type functions (GTF), compact expressions for the integrals over the spherical GTFs, and a simple method of derivation for the Talmi coefficients.(5) Ohers-Using relativistic model potential method we calculated potential curves for mercury dimer and performed molecular dynamic simulations which reproduced the liquid-solid phase transition. We have started a project of generating relativistic basis sets, in which the orbital exponents of GTFs are optimized without variational collapse.