Direct ab initio dynamics methods are using to study the H3PS ->(1) trans-H2PSH ->(2) cis-H2PSH, and H3PS ->(3) HPS + H-2 ->(4) PSH + H-2 reactions, The minimum energy paths (MEPs) of the two reaction channels, geometries, and harmonic vibrational frequencies for all stationary points and selected points along the MEPs are calculated using the QCISD/6-311++G(d,p) method. The single-point calculations are carried out by QCISD(T)/6-311++G(2df,2pd). The fitted three-parameter expressions of the calculated CVT/SCT and TST/Eckart rate coefficients in 200-2000 K for reactions (1) and (3) are k(1)(CVT/SCT) = 2.69 x 10(-42) T-16.52 exp(-9811.9/T) s(-1), k(1)(TST/Eckart) = 1.27 x 10(-31) T-13.39 exp(-12180.6/T) s(-1), k(3)(CVT/SCT) = 8.93 x 10(-20) T-9.82 exp(-20612.1/T) s(-1), and k(3)(TST/Eckart) = 1.31 X 10(-26) T-11.86 exp(-18896.4/T) s(-1), respectively. (c) 2005 Elsevier B.V. All rights reserved.