HO 2 rovibrational eigenvalue studies for nonzero angular momentum

Abstract

An efficient parallel algorithm is reported for determining all bound rovibrational energy levels for the HO 2 molecule for nonzero angular momentum values, Jϭ1, 2, and 3. Performance tests on the CRAY T3D indicate that the algorithm scales almost linearly when up to 128 processors are used. Sustained performance levels of up to 3.8 Gflops have been achieved using 128 processors for J ϭ3. The algorithm uses a direct product discrete variable representation ͑DVR͒ basis and the implicitly restarted Lanczos method ͑IRLM͒ of Sorensen to compute the eigenvalues of the polyatomic Hamiltonian. Since the IRLM is an iterative method, it does not require storage of the full Hamiltonian matrix-it only requires the multiplication of the Hamiltonian matrix by a vector. When the IRLM is combined with a formulation such as DVR, which produces a very sparse matrix, both memory and computation times can be reduced dramatically. This algorithm has the potential to achieve even higher performance levels for larger values of the total angular momentum.

Unimolecular rovibrational bound and resonance states for large angular momentum: J=20 calculations for HO2

“…The inspection of the energies shows that the agreement between them is quite satisfactory and six digits of relative accuracy have been achieved for all of the energies. For the low-lying bound states of the J = 2 case, we can also compare our calculations with Wu and Hayes's results 36 and with our previous LHFD calculations. 41 From Table I we can clearly see that the agreements among the four sets of calculations are very good.…”

“…The reader is referred to Wolfrum for some detailed comparisons. 29 On the theoretical side, calculations performed on three levels, namely, statistical theory ͑ST͒, classical trajectory ͑CT͒, and quantum mechanics ͑QMs͒, have been reported 11,21,[30][31][32][33][34][35][36][37] ͑not all the references have been listed here͒. The potential-energy surfaces ͑PESs͒ used are those by Melius and Blint, 38 Pastrana et al, 39 Kendrick and T Pack, 40 and Troe and co-workers.…”

“…The only other J Ͼ 0 calculations that have been reported are of the low-lying bound states by Wu and Hayes. 36 Part of the motivation for this work is to compare the quantum dissociation rates, k͑E , J͒, for higher J values with CT and ST results.…”

Converged quantum calculations of HO2 bound states and resonances for J=6 and 10

“…The only other J Ͼ0 calculations of the low bound states have been reported by Wu and Hayes. 11 For the unimolecular dissociation HO 2 →HϩO 2 , the quantum specific rate constants k(E,J) have been reported only for the Jϭ0 case. 12 Thus it will be interesting to compare the quantum dissociation rates k(E,J) for nonzero J with CT and ST results in this paper.…”

Calculating energy levels of isomerizing tetra-atomic molecules. I. The rovibrational bound states of Ar2HF

“…They decided to use the implicit sequential diagonalization and truncation approach. 35 In the present work we use more traditional explicit sequential diagonalization and truncation ͑see, for example, Ref. 33͒.…”