Using FireFly in education and research @ homeA short introduction in Computational Chemistry & an overview of strength possibilities of FireFl

Run a jobIf we wrote an input-file we can start a calculation. The command can be large, so you should use scripts/batch-files to lower complexity.

How to use MacMolPltFor a H2O calculation input- and output-file is manageable, but for bigger molecules our imagination is challenged. So it is us

Ok, at first we have to draw our molecule. Because MacMolPlt is very user-friendly controlling is very intuitive, so if you click thro

If you want special angles or bond length it is difficult to draw this in cartesian (x,y,z) coordinates. It is easier to work with z-matrices. For

Ok, now if your calculation is finished you can open output file with MacMolPlt.With the scrollbar at bottom you can see all optimization steps.For

When you want to calculate bigger molecules drawing could be very boring, so we can be happy about another function of our used visualization progr

In this chapter i collected some calculations which should give a little insight of possibilities with PC-Gamess and visualizing resul

If we want a structure optimization, calculation program search for structures which have lower energy. If program found a struct

When we get a minimum, we have to copy the coordinates into a new input file, but now with RUNTYP=HESSIAN in $CONTRL group.Results from thi

In freq table we saw an imaginary frequency, this is a vibration around a saddle point. Now he have to change geometry like this vib-mode.

This tutorial was written because computational chemistry applied in the right way has an enormous potential in research.Due to the lac

O.k. with this new structure we have no imaginary freq, but we can imagine that a trans-butadiene should be more stable as our found

A very nice and useful feature of MacMolPlt is visualization of Orbitals.We can see how i.e. HOMO/LUMO looks like of trans-butadiene.In MacMolPlt w

Now we should be able to optimize structures, so we should take the next step and see how to handle charged molecules with PC-Gamess.To advice pr

In the next step we try to calculate structure of a methyl-radical.To create this structure we could open methylamine file and delete the amine gro

In calculations it is sometimes necessary to “freez” some coordinates. I.e. when we will see where a proton will go if it is between NH3 and PH3.To

Instead of fixing atoms in space you can also fix bond length or angles.Here are two examples in which we want optimize H2O with a special O-H leng

PC-Gamess has another very interesting feature called Relaxed Surface Scan.With that tool you have a very useful possibility to study different cas

And here is the inputfile:Now its on you how to use this great tool in you research or education lessons.Examples-Relaxed Surface Scan $CONTRL RUNT

Till now in every $DATA group we had a C1 in 2nd line. This row declare symmetry of following molecule data. Point group symmetry C1

Examples-SymmetryTo realize why symmetry can be very useful here another example. Cr(C6H6)2C1 vs C6hcalculation time68 : 6minuteswith sameaccuracyP

Used ToolsTill now I tested some QM programs and visualization tools, and think that choosing the free available PC-Gamess/FireFly for calculat

Till now we used HF calculations only. But as we know HF have a lot of disadvantages so, we should use for research methods which contain electron

To instruct PC-Gamess to use Møller-Plesset-Perturbation in Second Orderwe have to add MPLEVL=2 in $CONTRL group.Examples-MPx & DFT $CONTRL SCF

If you want i.e. to get Energy difference between S0 & exciting state S1, you should optimize structure at first and then calculate exciting st

.. to be continued- CASSCF- and much more

This document is free available.It can be used for private or educational requirements.It must not be used for commercial aim without agreement of

PC-Gamess The PC GAMESS/Firefly is a freely available ab initio and DFT computational chemistry program developed to offer high performance o

MacMolPltMacMolPlt is a freely available modern graphics program for plotting 3-D molecular structures and normal modes (vibrations)

How to use PC-GamessAs said PC-Gamess/FireFly is an ab initio program, which reads molecular data and calculations settings and gives r

Input fileOk, lets start with an input-file.PC-Gamess/FireFly is very flexible, it contains a lot of setting possibilities. Both, system and calcul

Output fileOutput file is often a big file. If calculation was successful we get demanded informations, else we get hints why calculat

Punch filePunch file depends on run-type. For optimization i.e. it contains for every optimization step the coordinates and a $VEC group which is a