The connectivity is I-J-K-L, with J-K being the central “bond”. TORS dihedral angle (proper torsion) constraint between any four (different) atoms. BEND planar bend constraint between any three (different) atoms. STRE distance constraint between any two (different) atoms. H1, O, H2, can be given, but these must be unique in the input geometry. Where I, J, K, L refer to row numbers in the XYZ input. The updated z-matrix is printed in the log-file in each iteration.Ĭonstraint optimisations using the PQS optimizerĬonstraints can be be defined in an input block (with the OPTG command block) beginning with CONSTRAINT and ending with END. If the same variable is used in several places of the z-matrix and the corresponding new parameters are not the same, the variable is only kept in the first place, and the further ones are overwritten by the new fixed parameters. If the z-matrix contains constants, these may change and will be overwritten. In this case, all cartesian coordinates will be optimised, and in each iteration the new structure is back-transformed to the z-matrix. It is possible, however, to force pqs optimization by giving the optg option PQS or METHOD=PQS. Unfortunately, according to our current limited experience, the cluster optimization in pqsopt is neither well working in the original PQS program nor in Molpro and should therefore be used with care.īy default, optimizations with z-matrix geometry input are done with the old RF optimizer, and only the active variables in the z-matrix are optimised (cf. SCALE= value - Scaling factor for inverse distance coordinates. The section of the input which is needed for the geometry optimization must not modify variables that are used in the geometry definition (changes of such variables are ignored, and a warning message is printed). It is also possible to define procedures for the energy calculation, or to specify the first command from which the input should be repeated in each step (see section options to select the wavefunction and energy to be optimized). To save the results of the initial energy calculation, one can use, e.g., In addition, there is a variable OPTSTEP, which is incremented in each optimization step. Variables set by these programs as, e.g., ENERGY, are set as usual in each optimization step. The MP2 gradients will then be computed automatically.

For example, for MP2 gradients the commands HF and MP2 are needed. But the VARIABLE directive or option can be used to optimize, e.g., Davidson corrected energies, excited states, or counterpoise corrected energies.īy default the program repeats in each geometry optimization step those commands in the input that are needed to compute the last energy and any variable=value assignments in between the last energy calculation and the OPTG command. Normally, the last computed ground-state energy is used. Otherwise the gradient will be computed numerically from finite energy differences. See section analytical energy gradients for a list of methods with analytical gradients. When analytical gradients are available for the optimized energy these will be used. Please refer to the references section for citations of the analytic gradient methods. Reaction path following is described in F. For a detailed discussion of the various older minimization algorithms see F. This method is often advantageous in Transition State searches. Also available is the quadratic steepest descent following method of Sun and Ruedenberg (see J. Other available algorithms are based on the rational function approach and the geometry DIIS approach. Furthermore, it allows for constraint optimisations. It uses delocalized internal coordinates and converges often better than previous optimisers in Molpro.

Pulay (PQSOPT) is available in Molpro and used by default.

Since Molpro 2023.1 the optimizer developed by J. search for saddle points on energy surfaces), and reaction path following. search for equilibrium geometries), transition state optimization (i.e. Various optimization methods can be selected as described in section selecting the optimization method (METHOD). Furthermore, no procedures without an energy calculation must directly precede OPTG. HF, KS, MP2, etc.) are in a procedure, the OPTG must also be in the procedure. If the commands for the energy calculation (e.g. The OPTG command must be given after the energy calculation to which it refers. For minimum searches, it is usually sufficient to give just the OPTG command without further options or directives, but many options are available which are described in the following sections. The OPTG command can be used to perform automatic geometry optimizations for all kinds of wavefunctions. The OPT command available in previous MOLPRO versions is no longer needed and not available any more. Automatic geometry optimization is invoked using the OPTG command.

Zmatrix reference atoms suggestions