![]() This option requires a separate input section following the geometry specification. Geometry Specification & Modification Options ModRedundantĮxcept for any case when it is combined with the GIC option (see below), the ModRedundant option will add, delete, or modify redundant internal coordinate definitions (including scan and constraint information) before performing the calculation. If the code letter is omitted, then the variable's status remains the same as it was in the original molecule specification. Where variable is the name of a variable in the molecule specification, new-value is an optional new value to be assigned to it, and the final item is a one-letter code indicating whether the variable is to be active (i.e., optimized) or frozen the code letter D requests numerical differentiation be performed with respect to that variable and activates the variable automatically. Modification specifications for geometry optimizations using Z-matrix coordinates have the following form: variable A total of two input sections will be read: the first contains the charge and multiplicity, and the second contains alterations to the retrieved geometry. This option specifies that the geometry is to be taken from the checkpoint file and that modifications will be made to it. Use Geom=(Checkpoint,AddGIC) instead of Geom=Modify if you want to modify the generalized internal coordinates. ![]() In general, it is deprecated in favor of ModRedundant. Note that this option refers to modification specifications for geometry optimizations using Z-matrix coordinates only. Geom=Step=M is automatically converted to Geom=NGeom= M+1 if the previous optimization used redundant internal coordinates. NGeom= N retrieves the N th geometry from an optimization checkpoint file using the same record of points used for display in GaussView, where N=1 corresponds to the input molecule specification. Note that not all steps are always present in the checkpoint file a Hessian updated message in the log file means that the corresponding step is available in the checkpoint file. It must be combined with one of Checkpoint, AllCheck, or Modify. This option is used for restarting geometry optimization from intermediate points. Step=Original recovers the initial starting geometry. This option retrieves the structure produced by the N th step of a failed or partial geometry optimization (it is not valid for a successful optimization). This option is not valid with Modify but may be combined with ModRedundant, GIC, or AddGIC in the same way as the Checkpoint option. Thus, only the route section and any input required by keywords within it need be specified when using this option. Take the molecule specification (including variables), the charge and multiplicity, and the title section from the checkpoint file. ![]() Note that Geom=(Checkpoint,GIC) is equivalent to Geom=Checkpoint Opt=GIC, and Geom=(Checkpoint, ReadAllGIC) is equivalent to Geom=Checkpoint Opt=ReadAllGIC. The Geom=(Checkpoint,ReadAllGIC) option will not use the GICs from the checkpoint file, but instead, it will read a new set of GICs from the input file and calculate their values based on the current molecular specification (e.g., Cartesian coordinates) from the checkpoint file. The Geom=(Checkpoint,GIC) option (i.e., without ModRedundant) will not use the GICs from the checkpoint file, but instead, it will build a new set of GICs automatically based on the current molecular specification (e.g., Cartesian coordinates) from the checkpoint file. Note that Geom=(Checkpoint,ModRedundant,GIC) is equivalent to Geom=(Checkpoint, AddGIC). Checkpoint may be combined with the ModRedundant option or with the AddGIC option if you want to retrieve and alter the molecule specification in a checkpoint file using internal coordinate-style modifications. For example, Geom=Checkpoint may be used by a later job step to retrieve the geometry optimized during an earlier job step from the checkpoint file. ![]() Only the charge and multiplicity are read from the input stream. Take the molecule specification (including variables) from the checkpoint file. Options Geometry Retrieval Options Checkpoint ![]()
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