MOLPRO

CONTENTS
xxvi
42.2.7 Numerical Hessian (NUMHESS) . . . . . . . . . . . . . . . . . . . . . 313
42.2.8 Hessian elements (HESSELEM) . . . . . . . . . . . . . . . . . . . . . 314
42.2.9 Hessian update (UPDATE) . . . . . . . . . . . . . . . . . . . . . . . . 314
42.2.10 Numerical gradients (NUMERICAL) . . . . . . . . . . . . . . . . . . . 315
42.2.11 Transition state (saddle point) optimization (ROOT) . . . . . . . . . . . 315
42.2.12 Setting a maximum step size (STEP) . . . . . . . . . . . . . . . . . . 316
42.2.13 Redefining the trust ratio (TRUST) . . . . . . . . . . . . . . . . . . . . 316
42.2.14 Setting a cut parameter (CUT) . . . . . . . . . . . . . . . . . . . . . . 316
42.2.15 Line searching (LINESEARCH) . . . . . . . . . . . . . . . . . . . . . 316
42.2.16 Reaction path following options (OPTION) . . . . . . . . . . . . . . . 317
42.2.17 Optimizing energy variables (VARIABLE) . . . . . . . . . . . . . . . 317
42.2.18 Printing options (PRINT) . . . . . . . . . . . . . . . . . . . . . . . . 318
42.2.19 Conical Intersection optimization (CONICAL) . . . . . . . . . . . . . 318
42.3 Using the SLAPAF program for geometry optimization . . . . . . . . . . . . . 320
42.3.1 Defining constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
42.3.2 Defining internal coordinates . . . . . . . . . . . . . . . . . . . . . . . 322
42.3.3 Additional options for SLAPAF . . . . . . . . . . . . . . . . . . . . . 322
42.4 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
42.4.1 Simple HF optimization using Z-matrix . . . . . . . . . . . . . . . . . 323
42.4.2 Optimization using natural internal coordinates (BMAT) . . . . . . . . 324
42.4.3 MP2 optimization using a procedure . . . . . . . . . . . . . . . . . . . 324
42.4.4 Optimization using geometry DIIS . . . . . . . . . . . . . . . . . . . . 325
42.4.5 Transition state of the HCN – HNC isomerization . . . . . . . . . . . . 325
42.4.6 Reaction path of the HCN – HNC isomerization . . . . . . . . . . . . . 327
42.4.7 Optimizing counterpoise corrected energies . . . . . . . . . . . . . . . 329
43 VIBRATIONAL FREQUENCIES (FREQUENCIES) 334
43.1 Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
43.2 Printing options (PRINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
43.3 Saving the hessian and other information (SAVE) . . . . . . . . . . . . . . . . 336
43.4 Restarting a hessian/Frequency calculation (START) . . . . . . . . . . . . . . 336
43.5 Coordinates for numerical hessian calculations (COORD) . . . . . . . . . . . . 336
43.6 Stepsizes for numerical hessian calculations (STEP) . . . . . . . . . . . . . . . 336
43.7 Numerical hessian using energy variables (VARIABLE) . . . . . . . . . . . . . 336
43.8 Thermodynamical properties (THERMO) . . . . . . . . . . . . . . . . . . . . . 337
43.9 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337