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Double-ended minimum search by SCW (SCW)

Double-ended minimum search by SCW (SCW)

An extension of ADDF is the double-ended-ADDF (d-ADDF) method for efficient search of a single path connecting two given structures. In d-ADDF, an energy minimum on the scaled hypersphere is followed in the reverse direction with reducing the sphere radius. When two structures are connected by a single TS, the trace of ADDF path is expected to pass through a TS region. This d-ADDF guided TS search has been called two-point-SHS (2PSHS), and 2PSHS can find a TS between two adjacent MINs. A harmonic reference defined at the sphere center is no longer meaningful at a very long distance from the sphere center, and the trace of ADDF path may not pass through TS regions. Nevertheless, MINs can be found along the trace, and such a d-ADDF guided MIN search, which was called sphere contraction walk (SCW), can also find some MINs (intermediates) between given two structures. It is not guaranteed that all intermediates are obtained by a single application of SCW to two end points connected by a highly multistep and/or highly curved path, and one has to consider further applications of SCW to the pairs of MINs obtained in the first application. Finally, one can find a set of TSs connecting these intermediates by applying 2PSHS between adjacent pairs of MINs obtained by SCW.

An input file for formaldehyde is:

SCW/MP2/6-31G
 
0 1
C         -0.000000000000         -0.000000000000         -0.549482561269
O          0.000000000000          0.000000000000          0.708343639882
H          0.000000000000          0.934113144104         -1.131025039307
H         -0.000000000000         -0.934113144104         -1.131025039307
Reactant
C          0.000023803627         -0.008429382228         -0.993334032163
O         -0.000022033703          0.005182962475          0.738301273023
H         -0.000059778057          0.832236689203          1.250209901173
H         -0.000011799101         -0.813721500217          1.263147738321
 

Here, the upper structure is a product and the lower structure is a reactant. Structures, energies, spin expectation values, zero-point vibration energies (ZPVE), and normal mode eigenvalues of obtained intermediates (EQs) are listed in xxx_EQ_list.log file as:

List of Equilibrium Structures
 
# Geometry of EQ 0, SYMMETRY = C2v
C         -0.000000000000         -0.000000000000         -0.549482561269
O          0.000000000000          0.000000000000          0.708343639882
H          0.000000000000          0.934113144104         -1.131025039307
H         -0.000000000000         -0.934113144104         -1.131025039307
Energy    = -114.028691241420
S**2(SCF) =    0.000000000000
ZPVE      =    0.026886835902
Normal mode eigenvalues : nmode = 6
  0.054261405   0.062344303   0.086915179   0.106824536   0.345099764
  0.364995556
 
# Geometry of EQ 1, SYMMETRY = Cs
C         -0.000007563750          0.083927814345         -0.690783038876
O          0.000005574415         -0.074039964856          0.664371706039
H          0.000004533604          1.199361877206         -0.792250232396
H         -0.000002943345         -1.023608012668          0.910507233305
Energy    = -113.925629164680
S**2(SCF) =    0.000000000000
ZPVE      =    0.026321500963
Normal mode eigenvalues : nmode = 6
  0.047270924   0.053081100   0.057463925   0.086579063   0.315827536
  0.495408242

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Updated At:Feb. 13, 2018, 6:18 p.m.

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