Introduction: Calculation of Computational Quantum Mechanics

Computational calculations in chemistry and physics can reveal very interesting properties on some specimens (especially if they are subject to modification for better efficiency of a given original compound). in the procedures, besides factors of dipole moment, instability, electrostatic potential map, energy diagram and propabilistic reactivity calculations, where the use of computational quantum calculations shorten the laboratory time, making it clear and specific if the synthesis of a possible compound is viable. economically and temporally saying.


  • Quantum
  • Molecule modeling.
  • Molecular orbitals Orca Avogadro

Step 1: Computational Quantum Mechanics Calculation - Avogadro

  • As a first step, download Avogadro that has the possibility of input with Orca software.

In Avogadro software, you are guaranteed to create your molecules and optimize them by 99.9%; to avoid conflicts with the Ctrl + Alt + o command, which in turn does not guarantee proper molecular compression when using input extensions for Orca.

To optimize the molecule, first create the molecule of interest (obviously), then click on the E (note that under this E there is a down arrow), so a similar calculation will appear in the upper left corner of the screen containing the software.

Step 2: The Software Orca.

  • With this input properly done, click on the extensions tab, still referring to the Avogadro software, and look for the ORCA option.

Click on Advanced, when the screen for the creation of the input opens, and on Date mark the option MO and the second below. - LEAVE TWO MARKS - to get electron density and activated molecular orbitals during quantum calculations that Orca will perform - only input procedures ;)

After such procedure in the Basic tab, complete after the command:
! RHF SP def2-SVP

enter the code correctly / carefully ...

! Normalprint

% output

Print [P_Basis] 2

Print [P_MOs] 1


DETAIL, before performing such an operation download and install Orca on your computer!

After performing the above commands, click Create and save such a file. Inp in the folder where Orca is installed.
(Example: I installed Orca on my computer's C drive -> save the file inside your computer's C drive inside the Orca folder).

Step 3: In Cmd Run...

  • Open cmd and type:

cd C: \ Orca; Orca software is installed on your computer's C drive ...and press enter.

You will get a screen similar to the picture of this part, after such procedure, notice if the command is right by the script C: \\ Orca>
If this command is correct, type in front of the plus sign (>) the command:

orca.exe (the name of the molecule you saved in the Orca folder).inp > (the name of the molecule you saved in the Orca folder).out


After that press enter and wait ... In my case I missed the command several times because the multiplicity involved is an odd value and my number of electrons is also odd, if this happens change the multiplicity value to 2 in the previous step in Basic (in Avogadro software).

Step 4: Wait a Minute...

  • After the command is given, look for an underline on cmd's next command line.

if there is, WONDER, continuing ... Wait a while until the script term appears:

cd: \\ Orca_

To make sure your .out file was generated inside the Orca installation folder, the one where the input file created in Avogadro was saved.

After the calculation is done via cmd in Orca, look for the .out file in the Orca folder.
At this moment you can close your molecule (Avogadro) and cmd, in the end the quantum calculation has already been done ...

In the next step, open Avogadro again and in the open tab, look for the generated .out file and open it; you will see that there will be your molecule next to HOMO and LUMO Orbital values, drag the tab down a little and you will see that there are calculations for orbitals that will give around 100% optimization, as the image reveals.

...and have fun...