Implementation of polyatomic MCTDHF capability

The implementation of the Multiconfiguration Time-Dependent Hartree-Fock method for poly- atomic molecules using a cartesian product grid of sinc basis functions will be discussed. The focus will be on two key components of the method: first, the use of a resolution-of-the-identity approximation; sec- ond, the use of established techniques for triple Toeplitz matrix algebra using fast Fourier transform over distributed memory architectures (MPI 3D FFT). The scaling of two-electron matrix element transformations is converted from O(N⁴) to O(N log N) by including these components. Here N = n³, with n the number of points on a side. We test the prelim- inary implementation by calculating absorption spectra of small hydro- carbons, using approximately 16-512 points on a side.

This work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under the Early Career program, and by the offices of BES and Advanced Scientific Computing Research, under the SciDAC program.