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vibration_correlation_programs [2020/06/11 18:17] 127.0.0.1 external edit |
vibration_correlation_programs [2022/01/14 15:04] (current) rauhutdennisdinu [Rovibrational calculations] |
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====== Vibration correlation programs ====== | ====== Vibration correlation programs ====== | ||

+ | |||

===== The VCI program (VCI) ===== | ===== The VCI program (VCI) ===== | ||

- | ''[vci] | + | '' |

- | ''program and a basis of '' | + | ''or ''and a basis of ''or harmonic oscillator functions. For each vibrational state an individual ''\\ |

+ | T. Mathea, G. Rauhut, // | ||

+ | T. Petrenko, G. Rauhut, //A new efficient method for the calculation of interior eigenpairs and its application to vibrational structure problems//, [[https://\\ | ||

M. Neff, G. Rauhut, //Toward large scale vibrational configuration interaction calculations//, | M. Neff, G. Rauhut, //Toward large scale vibrational configuration interaction calculations//, | ||

M. Neff, T. Hrenar, D. Oschetzki, G. Rauhut, // | M. Neff, T. Hrenar, D. Oschetzki, G. Rauhut, // | ||

- | The anharmonic frequencies and intensities calculated by the '' | ||

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

- | VCI solutions can be obtained using a potential in grid representation,''POT=GRID'' (default), or in an analytical representation,. In the latter cases the ''be called prior to the ''VCI''in order to transform the potential. | + | * **''ANALYZE''=//or strongly mixed states in general (i.e. low VCI coefficients) a multi-state analysis can be performed, which prints major contributions of the VCI-vectors for all states in a certain window around the state of interest. Typically a window between 10 and 20% (i.e. ''ANALYZE''=0.1 or ''ANALYZE''=0.2) provides all the information needed. |

- | | + | * **''CIMAX''=//''CIMAX'' is the maximum excitation level corresponding to ''CITYPE''LEVEX''. In principle, a triple configuration $(1^42^43^4)$ would contribute to the VCI space. However, ''CIMAX=7'' restricts this to $(1^42^3)$, $(1^32^33^1)$,is ''CIMAX=12'' for 3D potentials and ''CIMAX=15'' for 4D potentials. |

- | By default, i.e. ''SADDLE=0'', the ''VCI''. Once the PES calculation has been started from a transition state, this information must be provided to the ''VCI'' program by using ''SADDLE=1''. Currently, the ''VCI'' program can only handle symmetrical double-minimum potentials. | + | * **''CITYPE''=//'' |

- | | + | * **'' |

- | Both, the grid-based and the analytical versions of the ''VCI''''implementations: | + | * **'' |

- | ''=3''which is the default) is a configuration selective and most efficient ''VCI'' program. ''VERSION=4'' is a conventional ''VCI'' program without configuration selection. It is thus computationally extremely demanding. | + | * **'' |

- | | + | * **'' |

- | '' | + | * **'' |

- | + | * **'' | |

- | '' | + | * **'' |

- | | + | * **'' |

- | ''CIMAX'' is the maximum excitation level corresponding to ''CITYPE''LEVEX''In principle, a triple configuration $(1^42^43^4)$ would contribute to the VCI space. However, ''CIMAX=7'' restricts this to $(1^42^3)$, $(1^32^33^1)$, $(1^32^23^2), ...$. The default is ''CIMAX=12''3D potentials and ''CIMAX=15''4D potentials. | + | * **'' |

- | | + | * **'' |

- | ''THRSEL'' controls the determination of the iterative configuration selection scheme. By default the wavefunction is considered to be converged once energy changes drop below ''THRSEL''02 cm$^{-1}$. | + | * **'''' |

- | + | * **''POT''=//the latter cases the ''to be called prior to the ''VSCF''VCI'' programs in order to transform the potential. | |

- | '' | + | * **''1'' |

- | + | * **'') ''the simultaneous calculation of several vibrational states, which is particularly useful in case of resonances. See also the option ''VCI program in connected with advanced features for the state assignment. | |

- | This thresholds controls the exclusion of selected configurations within the perturbative configuration selection criterion. The default is '' | + | * **''. However, only values less or equal to the one used in the surface calculation can be used. Default: ''NDIM=3''. |

- | + | * **''to 3. Note that '' | |

- | Within the perturbative selection criterion, unselected configurations are excluded from the procedure based on a criterion, which checks on the selection of configuration, | + | * **''$n$-body expansions of the polarizability tensor surfaces are truncated. The default is set to 0. Note that '' |

- | | + | * **''(=0 (off) Default) Once switched on (''1'') the configuration selection procedure acts on several states simultaneously. The number and identity of these states will be automatically determined. Be aware, that this option leads to a significant increase of CPU time due to enlarged correlation spaces. |

- | By default ''SELSCHEME''1, configurationis will be selected by a perturbative criterion. Alternative one may use a criterion based on 2$\times$2 VCI matrices (''SELSCHEME''=2). Usually the differences are extremely small and the matrix based criterion is slightly more time-consuming. | + | * **''$\mu$-tensor for calculating the vibrationally averaged rotational constants is truncated after the 2nd order terms, i.e. '' |

- | | + | * **''1'' |

- | Within the evaluation of the VCI integrals contraction schemes are used to reduce the computational effort. In the analytical VCI program values 0, 1 and 2 are supported, while in the grid based version only the options 0 and 1 exist. Memory demands and CPU speed-ups increase with increasing values. The default is set to 1. On machines with limited memory a value of 0 is recommended for this keyword. | + | * **''1''$\alpha$. ''2'', see the option ''. In addition the generalized VSCF property integrals, i.e. $\left < VSCF \left | q_i^r \right | VSCF \right >$ are printed. These integrals allow for the calculation of arbitrary vibrationally averaged properties once the property surfaces are available. Default: '' |

- | + | * **''default, ''REFERENCE=0'' the reference for all state-specific calculations is the vibrational ground-state configuration. This leads to a violation of the Brillouin condition, but often to also to faster convergence. ''REFERENCE=1'' uses the VSCF configuration as reference for generating all excited configurations. This is the proper way of doing it, but usually requests higher excitation levels. | |

- | '' | + | * **''SADDLE''=//n//** By default, i.e. ''the ''of the potential belongs to a local minimum. Once the PES calculation has been started from a transition state, this information must be provided to the '' |

- | ''(1) in [[vibrational SCF programs]]) as a pseudo-potential like contribution to the fine grid of the potential. In the analytical representation of the potential this will already be done in the '' | + | * **''By default ''the differences are extremely small and the matrix based criterion is slightly more time-consuming. |

+ | * **''wavefunction is used after the ITERth iteration step, as long as the energy difference between the energy eigenvalues of the last two iteration steps is less than THRDIAG (see below). SKIPDIAG=2 usually leads to appropriate results. | ||

+ | * **''SKIPSAVE''=//n//** In cases of small deviations with respect to the norm of the VMP2-like wavefunction,=0 (disabled). | ||

+ | * **''1 enables the use of prediagonalization of physically meaningful subspaces. | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'''' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **''This thresholds controls the exclusion of selected configurations within the perturbative configuration selection criterion. The default is '' | ||

+ | * **'' | ||

+ | * **''Within the perturbative selection criterion, unselected configurations are excluded from the procedure based on a criterion, which checks on the selection of configuration, | ||

+ | * **''UBOUND''//n//** Once overtones and combination bands shall be computed, the upper energy limit is controlled by the keyword ''UBOUND'', i.e. states, for which the harmonic estimate is larger than $n$, will not be computed. the default is set to $n$=5000 cm$^{-1}$. | ||

+ | * **''the ''the DAT2GR program (DAT2GR)|the DAT2GR program (DAT2GR)]]), the VCI program can be forced to compute just these states by the option ''1''. Note that the vibrational ground state will always be computed and needs not to be specified explicitly. | ||

+ | * **'''' | ||

+ | ''#]]) as a pseudo-potential like contribution to the fine grid of the potential. In the analytical representation of the potential this will already be done in the '' | ||

'' | '' | ||

'' | '' | ||

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'' | '' | ||

Note that the 1D and 2D corrections increase the computational cost considerably and are only available for non-linear molecules. | Note that the 1D and 2D corrections increase the computational cost considerably and are only available for non-linear molecules. | ||

+ | * **'' | ||

+ | '' | ||

- | By default the ''='' | + | ==== Rovibrational calculations ==== |

- | Once vibrational states have been defined with the ''VIBSTATE'' program (section [[vibrational SCF programs#, the VCI program can be forced to compute just these states by the option '' | + | ''ROVIB'',//options// |

- | Once overtones and combination bands shall be computed, the upper energy limit is controlled by the keyword ''UBOUND'', i.e. states, for which the harmonic estimate is larger than $n$, will not be computed. the default is set to $n$=5000 cm$^{-1}$. | + | By default, the ''the ''ROVIB'' directive allows for the calculation of rovibrational transitions for molecules with Abelian point groups. This includes also the IR intensities once dipole moment surfaces have been computed and Raman intensities if they are available and requested in the vibrational calculation. For details see:\\ |

+ | S. Erfort, M. Tschoepe, G. Rauhut, //Towards a fully automated calculation of rovibrational infrared intensities for semi-rigid polyatomic molecules//, J. Chem. Phys. **153**, xxxxxx (2020).\\ | ||

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

- | Rovibrational energy levels can be computed within the adiabatic rotation approximation (ARA). All energy levels for J-values up to $n$ will be calculated. | + | * **''Rovibrational levels can be computed for arbitrary numbers of J$=n$. This will perform a purely rotational calculation (RCI). To obtain approximate rovibrational energies, vibrational energies have to be added. |

+ | * **'' | ||

+ | * **'' | ||

+ | * **''within the calculation of the partition functions as needed in rovibrational calculations. By default a constant $\mu$-tensor is assumed. | ||

+ | * **'' | ||

+ | * **''(=$10^{-4}$ Default) Threshold for the relative deviation within the iterative determination of the rotational partition function. | ||

+ | * **''for the relative deviation within the iterative determination of the vibrational partition function. | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * '' | ||

+ | * ''J K \tau> = i^\sigma/-1)^{J+K+\tau}|J-K> | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **''to be set in order for rovibrational intensitites to be computed. | ||

+ | * **''$n$-mode expansion in the dipole surfaces used for vibrational transition moments in rovibrational intensities. | ||

+ | * **'' | ||

+ | * **''be switched on with '' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **'' | ||

+ | * **''. | ||

- | '' | ||

- | '' | ||

- | '' | ||

- | |||

- | The expansion of the potential in the '' | ||

- | |||

- | Term after which the $n$-body expansions of the dipole surfaces are truncated. The default is set to 3. Note that '' | ||

- | |||

- | Term after which the $n$-body expansions of the polarizability tensor surfaces are truncated. The default is set to 0. Note that '' | ||

- | |||

- | By default the symmetry of the molecule will be recognized automatically within the '' | ||

- | |||

- | This keyword specifies the reference for the definition of the configurations. By default, '' | ||

- | |||

- | By default all VCI calculations will employ ground-state based VSCF modals, '' | ||

- | |||

- | In the analytical configuration selective VCI program different diagonalization schemes can be used. '' | ||

- | |||

- | In case of resonances or strongly mixed states in general (i.e. low VCI coefficients) a multi-state analysis can be performed, which prints major contributions of the VCI-vectors for all states in a certain window around the state of interest. Typically a window between 10 and 20% (i.e. '' | ||

- | |||

- | By default the expansion of the $\mu$-tensor for calculating the vibrationally averaged rotational constants is truncated after the 2nd order terms, i.e. '' | ||

- | |||

- | This option provides an extended output. '' | ||

- | |||

- | If // | ||

- | |||

- | '' | ||

==== Explicit definition of the correlation space ==== | ==== Explicit definition of the correlation space ==== | ||

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mp2 | mp2 | ||

optg !(1) optimizes the geometry | optg !(1) optimizes the geometry | ||

- | frequencies, !(2) compute harmonic frequencies | + | frequencies, !(2) compute harmonic frequencies |

label1 | label1 | ||

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cphf,1} | cphf,1} | ||

- | {surf,, !(3) generate potential energy surface | + | {xsurf, !(3) generate potential energy surface |

| | ||

- | vscf !(4) do a VSCF calculation | + | poly |

- | vci, !(5) do a VCI calculation | + | vscf,!(4) do a VSCF calculation |

+ | vci,pot=poly, !(5) do a VCI calculation | ||

put, | put, | ||

| | ||

</ | </ | ||

- | The following input example for aan analytical calculation of anharmonic frequencies and intensities (1) optimizes the geometry of water, (2) computes the harmonic frequencies, | + | The following input example for an analytical calculation of anharmonic frequencies and intensities (1) optimizes the geometry of water, (2) computes the harmonic frequencies, |

< | < | ||

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mp2 | mp2 | ||

optg !(1) optimizes the geometry | optg !(1) optimizes the geometry | ||

- | frequencies, !(2) compute harmonic frequencies | + | frequencies, !(2) compute harmonic frequencies |

label1 | label1 | ||

Line 160: | Line 185: | ||

cphf,1} | cphf,1} | ||

- | {surf,, !(3) generate potential energy surface | + | {xsurf, !(3) generate potential energy surface |

| | ||

poly, | poly, | ||

| | ||

- | vscf,type=poly !(5) do a VSCF calculation | + | vscf,pot=poly !(5) do a VSCF calculation |

- | vci,type=poly, !(6) do a VCI calculation | + | vci,pot=poly, !(6) do a VCI calculation |

put, | put, | ||

| | ||

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

- | * **'' | ||

- | * **'' | ||

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

+ | * **'' | ||

+ | * **'' | ||

===== The vibrational MP2 program(VMP2) ===== | ===== The vibrational MP2 program(VMP2) ===== |