Single-point calculation

On e type of single point calculation, that of calculating vibration al properties, is distinguished as a vihmiions calculation in Ilyper-Chein. A lufcratilrui.s calculation predicts fun dam en tal vibrational frecinencies, m frared absorption in tensities, and norm al modes for a geometry optimized molecular structure. 

Specifies the calculation ofelectron correlation energy using the Mwllcr-i lessct second order perturbation theory (Ml 2). This option can only be applied Lo Single Point calculations. 

ZIXDO/S is parameteri/ed to reproduce spectroscopic transitions, therefore we do not recommend using this method for geometry optim i/ation. You can obtain better results by performing a single-point calculation wuth ZIXDO/S on a geometry obtained from the Model Builder, an optim Ization iisln g one of IlyperChem s oth er methods, or an external source. 

A single poinL calcnlaiion at the points b, c, d, or e will give a higher energy. E, than a single point calculation near the niini-mu ni at a. 

To go from a semiempirical calculation in the GAUSSIAN implementation (File 9-1) to an ab initio calculation, one need only change PM3 in the route section of the input file to sto-3g for a single point calculation or sto-3g opt for an optimization. We have made this change in File 10-1 along with the substitution of h for f in the second line of the geometry section to calculate the molecular... 

Procedure. Cany out the STO-3G single point calculations on H2 in a way similar to that of Exercise 10-9 at interatomic distances of 0.4 to 1.2 A at intervals of 0.1 A. This is best done in the z-mahix format, for example. 

The more recently developed methods define an energy expression for the combined calculation and then use that expression to compute gradients for a geometry optimization. Some of the earlier methods would use a simpler level of theory for the geometry optimization and then add additional energy corrections to a final single point calculation. The current generation is considered to be the superior technique. 

You can use a single point calculation that determines energies for ground and excited states, using configuration interaction, to predict frequencies and intensities of an electronic ultraviolet-visible spectrum. 

There are two types of Cl calculations implemented in Hyper-Chem — singly excited Cl and microstate CL The singly excited Cl which is available for both ab initio and semi-empirical calculations may be used to generate UV spectra and the microstate Cl available only for the semi-empirical methods in HyperChem is used to improve the wave function and energies including the electronic correlation. Only single point calculations can be performed in HyperChem using CL... 

HyperChem supports MP2 (second order Mpller-Plesset) correlation energy calculationsusing afe mi/io methods with anyavailable basis set. In order to save main memory and disk space, the HyperChem MP2 electron correlation calculation normally uses a so called frozen-core approximation, i.e. the inner shell (core) orbitals are omitted. A setting in CHEM.INI allows excitations from the core orbitals to be included if necessary (melted core). Only the single point calculation is available for this option. 

The concept of ghost-atoms only applies to Single Point calculations in the current version of HyperChem. 

HyperChem always computes the electronic properties for the molecule as the last step of a geometry optimization or molecular dynamics calculation. However, if you would like to perform a configuration interaction calculation at the optimized geometry, an additional single point calculation is required with the Cl option being turned on. 

Once you have calculated an ab initio or a semi-empirical wave function via a single point calculation, geometry optimization, molecular dynamics or vibrations, you can plot the electrostatic potential surrounding the molecule, the total electronic density, the spin density, one or more molecular orbitals /i, and the electron densities of individual orbitals You can examine orbital energies and select orbitals for plotting from an orbital energy level diagram. 

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