Development of the large scale computational program system based on the SAC-CI method

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The SAC/SAC-CI method was developed in 1978 and has been confirmed to be a powerful tool for investigating the molecular excited states through the large numbers of applications. In this project, we have developed the largescale computational program system based on the SAC/SAC-CI method and performed some applications. The original program code (SAC85) is improved with respect to the algorithm, structure, and utility. Some new functions are also developed and installed in the new version of the program system.(1)Acceleration of the program code :We improve some algorithms of the program code and vectorize some of them to achieve the high performance on the vector processor machine. The acceleration is mainly performed for the codes constructing the Hamiltonian matrix elements and the diagonalization step. For the former, we propose the different algorithm from the original one and succeded in c.a.five-times acceleration. For the latter, iterative diagonalization code is vectorized and … More it becomes c.a.20 times faster than the original one. In addition, improvement of the convergence results in c.a.10times acceleration. Furthermore, it enables to calculate the large number of solutions which were not obtained by the previous algorithm.(2)Modification for workstation :Now, workstations is widely prevailed for the ab initio MO calculation. SAC-CI program system is modified to be executed on the unix machine. To this end, all the file input/output is performed automatically and the required amount of memory is automatically allocated in the new version of the program system.(3)New functions :We develope the method for calculating the analytical energy gradients for the ground, excited, ionized, and electron attached states by the SAC/SAC-Ci method. Original program code is limited to the applications to the single-electron process and to the low-spin states from singlet to triplet. In the new version, applications to the multiple electron process and the high-spin states from quartet to septet are also available.(4)Utility :Input and output of the progaram system are modified to be user-friendly. Optimal values are set to default and unimportant parameters are excluded from the iput. Program manual is rearranged in accordance with the new input and the structure of the program system is explained in detail. Output is also modified to be simple and clear for the general user. Less