Single Point Calculation

The results of single point calculations are in SinglePointCalculation class.

Example

The optimizied geometry of ethylene was used to calculate the electronic transitions, these can be useful for predicting UV-VIS spectrum.

The ORCA output is in the ethylene_uvvis.out file, let’s see how we can parse it!

# import PyORCA
import pyorca as po

# parse the ORCA output file
data = po.OrcaOutput.parse_file('ethylene_uvvis.out')

# check that the calculation terminated normally
assert(data.terminated_normally)

# this output file contains only single calculations, the TD-DFT calculation
print('Number of calculations:', len(data.calculations))
print()

# get the information about electronic spectrum
electronic_spectrum = data.calculations[0].electronic_spectrum

# print the wavelengths and intensities of electronic transitions
print('Electronic transitions:')
for wavelength, intensity in zip(electronic_spectrum.wavelengths, electronic_spectrum.intensities):
    print(f'{wavelength:0.1f} nm (relative intensity {intensity:0.4f})')

Number of calculations: 1

Electronic transitions:
153.3 nm (relative intensity 0.0000)
152.2 nm (relative intensity 0.0141)
148.3 nm (relative intensity 0.5309)
142.6 nm (relative intensity 0.0000)
138.5 nm (relative intensity 0.0000)
127.9 nm (relative intensity 0.0000)
119.5 nm (relative intensity 0.0000)
117.8 nm (relative intensity 0.0000)
111.6 nm (relative intensity 0.0000)
110.7 nm (relative intensity 0.2355)

The experimental UV-VIS spectrum of ethylene has absorption maximum around 261 nm, so it seems that simple B3LYP/def2-TZVP doesn’t give us very good estimate.