# Differences

This shows you the differences between two versions of the page.

pes_transformations [2020/06/11 18:17] 127.0.0.1 external edit |
pes_transformations [2020/07/15 15:32] (current) qianli |
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====== PES transformations ====== | ====== PES transformations ====== | ||

- | Once a potential energy surface (PES) has been generated by the ''program, it can be transformed to different representations. The first possibility is a representation by basis functions, i.e. the '' | + | Once a potential energy surface (PES) has been generated by the ''or '', it can be transformed to different representations. The first possibility ([[PES transformations#is a representation by basis functions, i.e. the ''([[PES transformations#may be altered by the ''([[PES transformations#offers a transformation of the PES for vibrational structure calculations of isotopologues or Franck-Condon factors. |

===== Analytical representations (POLY) ===== | ===== Analytical representations (POLY) ===== | ||

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'' | '' | ||

- | The '' | + | The ''by polynomials,. Once an analytical representation has been chosen, the corresponding VSCF, VCI or VMP2 programs need to be selected (see below). There are different versions of the ''. An example for the use of the ''\\ |

+ | B. Ziegler, G. Rauhut, //Efficient generation of sum-of-products representations of high-dimensional potential energy surfaces based on multimode expansions.//,\\ | ||

The following //options// are available: | The following //options// are available: | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

* **'' | * **'' | ||

* **'' | * **'' | ||

* **'' | * **'' | ||

* **'' | * **'' | ||

- | * **''POT'' | + | * **''NVARC''For the calculation of vibrationally averaged rotational constants $\mu$-tensor surfaces will be generated and transformed to polynomials up to 2nd order (default). The order can be changed by the integer passed to the ''NVARC'' keyword. |

- | * **''''(=7 Default) This keyword controls the minium number of basis functions to be used. | + | |

- | * **'' | + | |

- | * **''-quartic force field, i.e. '' | + | |

- | * **''surfaces have been computed, they need to be transformed to a analytical representation as well. This can be accomplished by ''DIPOLE=1'' and will be set by default, if dipole surfaces are available. ''. | + | |

* **'' | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

* **'' | * **'' | ||

- | * **''ADDZERO''Within the fitting of the grid representation the expansion point usually is not included. In certain cases in might be meaningful to include it. This can be accomplished by ''=1'' | + | * **''VERSION''(n=1,2,3) By default ''VERSION=2'' will be used in combination with the ''SURF'' program, while the most generalized version, i.e. ''VERSION=3'', will be used by default for the ''XSURF'' program. ''can be used in combination with the ''XSURF''and uses conventional fitting (no Kronecker products). |

- | * **'', 3D or 4D surfaces from the multi-mode expansion of the potential, the ''DELAUTO'' keyword sets all coefficients of the polynomial expansion of these surfaces to zero. The threshold passed to the ''DELAUTO'' keyword corresponds to the $\chi^2$ value of the least squares fitting procedure. It acts on both, the energy and the dipole surfaces. The default is set to 9.d99, i.e. all surfaces with $\chi^2$ values below this threshold will not be affected. | + | * **''Note that VRCs are not supported by the '' |

- | * **''NVARC''=//n//** For the calculation of vibrationally averaged rotational constants $\mu$-tensor surfaces will be generated and transformed to polynomials up to 2nd order (default). The order can be changed by the integer passed to the ''NVARC'' keyword. This transformation can also be extended within the ''VSCF'' | + | |

- | * **'' | + | |

- | * **'' | + | |

- | * **'' | + | |

- | * **''by default for the ''. //. | + | |

==== Plotting of 3D surfaces ==== | ==== Plotting of 3D surfaces ==== | ||

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The following //options// are available: | The following //options// are available: | ||

+ | * **'' | ||

* **'' | * **'' | ||

* **'' | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

'' | '' | ||

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'' | '' | ||

- | The '' | + | The '', which is recommended. These features are only relevant for the simulation of vibronic spectra as one has to deal with several PESs in the same input. For simple VCI calculations, |

The following //options// are available: | The following //options// are available: | ||

- | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

===== Grid to grid transformations (VGRID) ===== | ===== Grid to grid transformations (VGRID) ===== | ||

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'' | '' | ||

- | For certain applications a finer grid may be needed than generated by the '' | + | For certain applications a finer grid may be needed than generated by the ''. There is no need for calling the ''.\\ |

The following //options// are available: | The following //options// are available: | ||

- | * **'' | ||

- | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

===== Transformation of the coordinate system (PESTRANS) ===== | ===== Transformation of the coordinate system (PESTRANS) ===== | ||

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'' | '' | ||

- | The '' | + | The ''. Due to that a completely different ''. For further details see:\\ |

P. Meier, D. Oschetzki, R. Berger, G. Rauhut, // | P. Meier, D. Oschetzki, R. Berger, G. Rauhut, // | ||

The following //options// are available: | The following //options// are available: | ||

- | * **'' | ||

- | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

- | * **'' | ||

- | * **'' | ||

* **'' | * **'' | ||

- | * **''tranformed potential. The information of the original potential will be taken from the the '' | + | * **'' |

+ | * **''transformed potential. The information of the original potential will be taken from the the ''. | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **''. | ||

Most keywords and directives of the '' | Most keywords and directives of the '' |