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Using FireFly in education and research @ home

A short introduction in Computational Chemistry & an overview of strength

possibilities of PC-Gamess/FireFly and how to make calculations more efficient

Part II Benchmark Basis/Correlation Correction

v 1.05

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This benchmark on basis set was done because calculation time strongly

depends on basis set.

There are a lot of different sets which describes chemical behaviour, some with

good approximation to real functions and some with acceptable description.

Smaller systems can be handled with large basis sets, but if we want to assay a

molecule with more typical size we have to make some arrangements to handle

such calculations. To see which smaller basis sets gave comparable

descriptions to bigger ones in less computational effort there were done some

benchmarks on typical molecules. We will also see when it is necessary to use

bigger sets. This may help to get a feeling how calculation time rise with large

basis sets.

M. Checinski

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Benchmarks of Basis/Correlation Correction

In this Chapter are the benchmarks collected, which i made to decide which basis sets

and Correlation Corrections are useful (quality & time consumption) for typical

questions in laboratory or which one should be used for educational demands.

For making a general statement about a good Basisset/Correlation Correction for

smaller computer(-cluster) it seems to be useful to compare different chemical

environments. We will study typical organic and inorganic molecules, to find out which

basis sets are not advisable for some structures.

Who just want to see the result should jump to the end of this chapter. There is a kindof summary.

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At first we need an imagination of influence of basis sets on computation time.

Because there are so many factors which have an influence on computational time it is

impossible to say i.e. one set need two and a half times more computation time than an

other. But to see how the tendency is i made a comparison of n-alkanes, to see how

influence of an additional CH2-Group is.

Benchmarks of Basis/Correlation Correction

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Here we see that different sets have different slopes.

There are hough differences in computational time of a C8-Alkane computed with a MINI

and a cc-pVTZ set (here 1:100).

c2 c3 c4 c5 c6 c7 c8

0,0

200,0

400,0

600,0

800,0

1000,0

Dependence of basis set on computation time of alkanes

MINI

3N21

6N31

6N31_dp

6N311

6N311_dp

6N311_2d2p

TZV_2d2p

cct

Benchmarks of Basis/Correlation Correction

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Here we see that a pd-polarized split-valence set needs more computation time than an

unpolarized triple-valence set.

c2 c3 c4 c5 c6 c7 c8

-50,0

50,0

150,0

250,0

350,0

Dependence of basis set on computation time of alkanes

MINI

3N21

6N31

6N31_dp

6N311

6N311_dp

6N311_2d2p

TZV_2d2p

cct

Benchmarks of Basis/Correlation Correction

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To compare the basis sets qualitatively we need some properties, which we can

compare.

As we have seen the absolute value of total Energy is not the only importantinformation, difference of total Energy by stretching a bond could give a good hint

Another property can be the dipole moment, which depends on bond partners and bond

length. But we can only compare dipole moments with real ones if the molecule were

measured in gas phase.

PC-Gamess gives us thermodynamic properties, too. But here we should, compare

comparable (gas phase) molecules, too.

We will take a focus on 1D-Potential Energy Surfaces and dipole moment.

Benchmarks of Basis/Correlation Correction

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At first we will discuss the behaviour of simplest alkane.

In previous chapters we have discussed the differences of RHF/UHF and HF in general.We have discussed about the cheap correlation correction of Moller-Plesset and the

popular hybrid calculation of DFT (especial Becke3-LeeYoungParr). Now we will try to

compare them qualitatively.

For that we study energy changing by C-H Bond stretching.

We compare how a HF, HF/MP2 and B3LYP influence the description of this system.

As basis sets we use the small split valence set 3-21 and the hough triple valence set

aug-cc-pTVZ with additional diffuse and polarized functions.

After that we will compare how the popular sets describe bond-stretching of many

different molecules at UHF/B3LYP level.

Benchmarks of Basis/Correlation Correction

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Ok, let's start with the 3-21 set.

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

0,00

0,05

0,10

0,15

0,20

0,25

Methan: stretch of C-H Bond

3N21-RHF

3N21-UHF3N21-RHF-MP2

3N21-RHF-B3L

3N21-UHF-B3Lx

3N21-UHF-B3L

distance to equibrillium length

energydifferencetolowestenergy

What we can see is that at HF level the description is significant different.

On the other hand all calculations say that the equilibrium bond distance (at 0.05 A stepping) have relative the

lowest energy. We will later see that this have not be ususal, but this system is easy to describe.

And we shall not forget that all basis sets were fitted on such general Molecules to give good functions.

Benchmarks of Basis/Correlation Correction

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To see better how the different calculations differs we should look at a smaller part of this diagram.

Here we see that we have three groups ( HF, HF/MP2 and DFT ). For this system the MP2 correction is comparable to

the computational heavier B3LYP calculation.

0,550 0,600 0,650

0,075

0,085

0,095

0,105

Methan: stretch of C-H Bond

3N21-RHF3N21-UHF

3N21-RHF-MP2

3N21-RHF-B3L

3N21-UHF-B3Lx

3N21-UHF-B3L

distance to equibrillium length

energydifferenc

etolowestenergy

Benchmarks of Basis/Correlation Correction

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If we use the hough aug-cc-pTZV set we see comparable descriptions of such bond-stretching.

But now the MP2 correction is not such good like in previous topic.

0,550 0,600 0,650

0,075

0,085

0,095

0,105

Methan: stretch of C-H Bond

aug-cc-pvtz-RHFaug-cc-pvtz-UHF

aug-cc-pvtz-RHF-MP2

aug-cc-pvtz-RHF-B3L

aug-cc-pvtz-UHF-B3L

aug-cc-pvtz-UHF-B3Lx

distance to equibrillium length

energydifferencetolowestenergy

Benchmarks of Basis/Correlation Correction

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Ok, lets put these descriptions together

Here we see that the ACCT set is much better than 3-21, but this is nothing unexpected =) if

we know that the ACCT set has for each Orbital 3 possible Orbitals which can be mixed and additional polarization

and diffuse functions, to make the resulting Orbital more perfect for this chemical environment.

Don't forget that this is a relative description, absolute values for ACCD are much lower than for 3-21.

1,000 1,100 1,2000,145

0,165

0,185

Methan: stretch of C-H Bond

3N21-RHF

3N21-RHF-MP2

3N21-UHF-B3L

aug-cc-pvtz-RHF

aug-cc-pvtz-RHF-MP2

aug-cc-pvtz-UHF-B3Lx

distance to equibrillium length

energydifferen

cetolowestenergy

Benchmarks of Basis/Correlation Correction

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At this point we should look at the computation effort of these calculations.

For better comparison we use a here a quite good information which we get from PC-Gamess on each calculation.

The CPU utilization should be around 100% (or like here on a dual-core 200%), higher values means 100% :)

But if we have lower values, that means HDD operations which are very very slow. In other words CPU have to wait

for data to make next Operation. We will later see how dramatically this could be and how PC-Gamess settings can

help us to avoid such problems. Ok, lets compare the WALL CLOCK times.

Here we see a big difference between calculation with ACCT and 3-21, on UHF/B3LYPx level where the utilizations

are most comparable we see a computational difference of 70:1 ! Ok, 12 minutes are not so long, but this is just a

very small Molecule. For usual molecules it is a hough difference.

At this point i have to say what B3Lx means. As mentioned PC-Gamess gives us a great flexibility in controlling

calculations, some less accurate settings seems to make descriptions worser but other have low effects in qualitativedescriptions but big in computational effort. I tested some settings with different molecules to check how to safe

computational time with small loss of accuracy. In another chapter i will summarize these settings.

The difference of B3Lx and B3L is just a smaller value of NRAD in \$DFT part.

This is by the way one cause why i made such benchmarks, to check which sets & settings gives best agreement in

accuracy and time consumption.

3N21-RHF 3N21-UHF 3N21-RHF-MP2 3N21-RHF-B3L 3N21-UHF-B3Lx 3N21-UHF-B3L

0,3 0,4 0,5 15,1 10,2 29,0

228,60% 225,02% 214,35% 200,45% 200,24 200,25%

349,9 412,3 823,5 496,6 706,1188,05% 186,20% 181,34% 192,95% 197,66%

Zeit [sec]

Util 2 CPU

aug-cc-pvtz-RHF aug-cc-pvtz-UHF aug-cc-pvtz-RHF-MP2 aug-cc-pvtz-RHF-B3L aug-cc-pvtz-UHF-B3Lx aug-cc-pvtz-UHF-B3L

Zeit [sec]Util 2 CPU

Benchmarks of Basis/Correlation Correction

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To see how the absolute differences are here are some impressions of methan.

There are hough differences between STO2/MINI and a mulit valence set.

Differences between bigger sets are in another scale.

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-40,40

-39,90

-39,40

-38,90

Methan: stretch of C-H Bond

STO2G

MINI

6N31-2pd

6N311-3p2d

cc-pVDZ

aug-cc-pVTZ

distance to equibrillium length

energydifferencetolowestenergy

Benchmarks of Basis/Correlation Correction

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Here we see that split-valence- and triple-valence-sets are compareable.

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-40,50

-40,30

Methan: stretch of C-H Bond

6N31-2pd

6N311-3p2dcc-pVDZ

aug-cc-pVTZ

distance to equibrillium length

energydifferencetolowestenergy

Benchmarks of Basis/Correlation Correction

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Here we see difference between HF / HF-MP2 / HF-B3LYP . Basis is 3-21.

Here there are no differences between RHF & UHF, RHF/B3L & UHF/B3L , and there are low differences between

RHF/B3L UHF/B3L & UHF/B3Lx

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-40,30

-39,80

Methan: stretch of C-H Bond

3N21-RHF

3N21-UHF3N21-RHF-MP2

3N21-RHF-B3L

3N21-UHF-B3Lx

3N21-UHF-B3L

distance to equibrillium length

energydifferencetolowestenergy

Benchmarks of Basis/Correlation Correction

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-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,30

0,000

0,050

0,100

0,150

0,200

0,250

C-C stretch of Ethan

distance to equilibrium lenght [A]

energyrelativetogroundstateE

Ok, with this experience we see that we should use UHF/B3Lx calculations.

Now we can start to assay other chemical environments. Let's check how different basis sets describe C-C Bond

breaking/creating on Ethan, which is a daily topic in Research.

Benchmarks of Basis/Correlation Correction

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At first we see, that the STO-2G & MINI set is significant different from the other.

Ethan C-C-Bond is a very simple system, and if these sets have such quality

problems, we should use them only for didactical usage or fast geometry pre-

optimization.

To put focus only the Basis sets, we use a PM3 optimized geometry for this calculation

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-0,04

0,06

0,16

0,26

Ethan: variation of C-C Bondlength

STO-2

MINIMIDI

3N21

DZV

6N31-2pd

TZV

6N311-3p2d

ACCD

Benchmarks of Basis/Correlation Correction

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For small stretch lengths we see that sets with no polarization functions seem not to be very accurate.

Another informations is that from STO-2 to DZV the relative energy minimum is 0.05 A from equilibrium geometry of

PM3 optimization.

To compare the other we should look at some smaller parts of the diagram.

0,05 0,10 0,15

-0,002

0,003

0,008

Ethan: variation of C-C Bondlength

STO-2

MINI

MIDI

3N21

DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

h k f l

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On length around 0.5 A we have another picture. The order of sets is a little bit mixed.

ACCT, ACCD, 6-311, TZV, DZV builds a close group. 6-31, 3-21 are not far away.

The MIDI set is a little bit far away and seems to calculate this environment worser than 3-21

0,45 0,50 0,550,047

0,052

0,057

0,062

0,067

Ethan: variation of C-C Bondlength

STO-2

MINI

MIDI3N21

DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

B h k f B i /C l ti C ti

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On a distance of ~ 1 A we can compare this situation with a interaction of 2 Methyl radicals.

Here we see that the hough sets give lowest energy configuration, for such special environment it's not unusual that

a set with so many additional Functions and Polarized & Diffuse-functions can describe this situation better.

Not far away are the split valence sets 6-31 and the 3-21.

0,95 1,00 1,05

0,123

0,128

0,133

0,138

Ethan: variation of C-C Bondlength

STO-2

MINI

MIDI

3N21DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

B h k f B i /C l ti C ti

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Factor time in computational chemistry shall not be underestaminate.

For this computation we can say that the MINI and STO-2 is qualitatively different.

The MIDI and 3-21 set is qualitatively comparable to the bigger sets.

For bigger molecules or a fast preview (or a slow cpu) they are a good agreement.

Shown time relationship is not exact portable to other calculations, there are so many

parameters which influence the calculations, but we can say the tendency is accepteable.

The most CPU utilizations were ~ 100% per CPU, but the higher the molecule and the basis set is the

larger is the number of stored Integrals. If they are larger than given RAM-Size they have to be

stored to HDD with the consequence that the CPU utilization breaks significant down and the CPU

time rise a lot, as seen for the ACCT calculation.

To give a feeling how important this can be, we can see if we compare the same calculation with

different RAM access. (MW for \$SYSTEM MWORDS=xxx \$END)

For a better recapitulation we shall compare the computational time.

~ x times faster

STO-2 MINI MIDI 3N21 DZV 6N31-2pd TZV 6N311-3p2d ACCD ACCT

Zeit 13,8 13,5 22,9 22,4 62,9 76,9 140,8 216,0 219,0

Util 2 CPU 186,41% 200,41% 199,85% 199,75% 195,20% 198,73% 195,31% 193,34% 191,59%

ACCT MW=180 MW=380

Zeit 17524,6

38,77%Util 2 CPU

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,300,000

0,050

0,100

0,150

0,200

0,250

C-H stretch of Acrolein

distance to equilibrium lenght [A]

energyrelativetogroundstateE

As next we prove the basis sets on Acrolein.

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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At first we see, that the STO-2G & MINI set is significant different from the other,

again. With such quality problems, we should use them only for didactical usage or

fast geometry pre-optimization (organic molecules only).

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-0,04

0,06

0,16

0,26

Acrolein : Vinyl(CO)-H bond stretch

STO-2

MINI

MIDI3N21

DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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On bond length near the equilibrium geometry of a PM3 optimized Acrolein we see

that many sets haven't their minima.

0,00 0,05 0,10 0,15-0,002

0,003

0,008

Acrolein : Vinyl(CO)-H bond stretch

STO-2

MINI

MIDI

3N21

DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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Here we see the known groups.

For better interpretation we should look two pages later on the total energies.

0,45 0,50 0,55

0,047

0,052

0,057

0,062

0,067

Acrolein : Vinyl(CO)-H bond stretch

STO-2

MINI

MIDI3N21

DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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The same situation on long distances. The triple valence sets (TZV, 6-311, CCT) and

some split valence sets (6-31, DZV, ACCD) runs parallel. STO-2G, MINI, MIDI are far

away or like 3-21 run qualitatively in another way .

For a better comparison we should look at the total energy at a distance of 1 A.

MIDI 3N21 6N31-2pd TZV-2pd 6N311-3p2d CCD CCT ACCD ACCT

-190,67140 -190,73610 -191,83155 -191,80680 -191,87138 -191,86636 -191,81550 -191,87677 -191,83076 -191,88065

DZV-pd

E at 1 A

0,95 1,00 1,05

0,108

0,113

0,118

0,123

Acrolein : Vinyl(CO)-H bond stretch

STO-2

MINI

MIDI

3N21DZV-pd

6N31-2pd

TZV-2pd

6N311-3p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

Benchmarks of Basis/Correlation Correction

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STO-2G MINI MIDI 3N21

Energie -183,80257 -190,60694 -190,77909 -190,84962

Zeit 23,2 25,4 49,9 45,5

Ut il 2 CPU 200,04% 200,19% 200,09% 200,05%

DZV-pd 6N31-2pd TZV-2pd 6N311-3p2d CCD CCT ACCD ACCT

Energie -191,94875 -191,92146 -191,98662 -191,98066 -191,92643 -191,99154 -191,94354

Zeit 142,7 173,5 242,7 455,9 137,3 1016,8 447,6

Ut il 2 CPU 199,39% 198,91% 196,42% 197,38% 199,18% 195,97% 196,03%

Here we see again how bigger sets rise computational time and which additional effect cpu

utilization can have on wall clock.

If we compare the energies of triple and split valence we see a little difference, this is not unusual

because we have a bigger set on inner and outer orbitals. If we find better inner orbitals with triple

valence set we will always find lower energy, even if the outer chemical Orbitals are like from a

split valence.With this assay on acrolein we can make a first conclusion.

STO-2G, MINI & MIDI is good for fast calculations, we will see later that even this sets describes i.e.

oxidation of ethan with peroxoaceticacid in a right way.

But if we will make research more serious we should use at least a 6-31(pd) set.

Now let's compare computational effort.

Benchmarks of Basis/Correlation Correction

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-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,300,000

0,050

0,100

0,150

0,200

0,250

1-Cl-Propen : HCCl=CHMe bond stretch

distance to equilibrium lenght [A]

energyrelativeto

groundstateE

Here we test trans-1-Cl-Propen

Benchmarks of Basis/Correlation Correction

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-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

-0,10

0,00

0,10

0,20

0,30

0,40

1-Cl-Propen : HCCl=CHMe bond stretch

STO-2

MINI

MIDI

3N21

6N31

6N31-pd

DZV-pd

TZV-2p2d

6N311-2p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

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0,45 0,50 0,55

0,105

0,115

0,125

0,135

1-Cl-Propen : HCCl=CHMe bond stretch

STO-2

MINI

MIDI

3N21

6N31

6N31-pd

DZV-pd

TZV-2p2d

6N311-2p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

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0,95 1,00 1,05

0,24

0,25

0,26

0,27

1-Cl-Propen : HCCl=CHMe bond stretch

STO-2

MINI

MIDI

3N21

6N31

6N31-pd

DZV-pd

TZV-2p2d

6N311-2p2d

CCD

CCT

ACCD

ACCT

Benchmarks of Basis/Correlation Correction

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STO-2G MINI MIDI 3N21

Energie -555,3482 -574,5341 -574,6387 -574,6706

Zeit [min] 0,5 0,6 1,2 1,2

Util 2 CPU 200,16 200,2 200 200,06

6N31 6N31-pd DZV-pd TZV-2p2d 6N311-2p2d CCD CCT ACCD ACCT

Energie -577,4500 -577,5057 -577,5326 -577,5850 -577,5795 -577,5401 -577,5949 -577,5507 -577,5974

Zeit 1,6 3,6 3,8 11,6 10,0 4,3 27,2 18,9 240

Util 2 CPU 200,01% 199,95% 199,99% 199,98% 199,97% 199,95% 199,97% 199,94% 199,97%

MIDI 3N21 DZV-pd 6N31-pd TZV-2pd 6N311-3p2d CCD CCT ACCD ACCT

E at 1 A -574,3811 -574,4115 -577,2856 -577,2496 -577,3339 -577,3258 -577,2884 -577,3425 -577,3028 -577,3464

Here is the corresponding data.

The cpu utilization is comparable, so we can better compare computation time now.

I.e. we get much better description with aug-cc-pVTZ set in comparison to 3-21 but it tooks 200times more computational time.

Benchmarks of Basis/Correlation Correction

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Now lets take a look at an classical inorganic Molecule

-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,30

0,000

0,050

0,100

0,150

0,200

0,250

3OCNi-CO stretch of Ni(CO)4

distance to equilibrium lenght [A]

energyrelativeto

groundstateE

Benchmarks of Basis/Correlation Correction

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The structure was taken by a TZV-dp UHF/B3Lx optimization.

Here we see the problem of today basis sets in inorganic chemistry.

There are so many orbitally changing in the metallic sphere that we need a hough

choice of functions for every orbital to find a good approximation of the real one.

-0,30 -0,10 0,10 0,30 0,50 0,70 0,90 1,10 1,30

0,00

0,05

0,10

Ni(CO)4: Variation of 3(OC)Ni-CO

MINI

MIDI

3N21

6N31

6N31-dp

6N31-2d2p

TZV

TZV-dp

TZV-2d2p

Mhs-tm

Mhs-ptm

Cct

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As we see, there are much bigger differences in qualitative description of an OC Ni interaction, than

in organic molecules. MINI & MIDI set have even a 0.10 A shorter equilibrium Bondlength and a

significant different description. In principle it is useful, but in comparison to other there are bad.

The same apply to 3-21 set.

When we assay effect of polarization functions we see even at small bond-stretch differences.

0,05 0,10 0,15

0,000

0,010

0,020

Ni(CO)4: Variation of 3(OC)Ni-CO

MINI

MIDI

3N21

6N31

6N31-dp

6N31-2d2p

TZV

TZV-dpTZV-2d2p

Mhs-tm

Mhs-ptm

Cct

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We also see that a split set of polarization functions has lower effects than one set.

But if we compare computational effort we see a kind of doubling cpu time.

6N31 6N31-dp 6N31-2d2p TZV TZV-dp TZV-2d2p

Zeit [s] 225,7 582,6 1382,7 739,2 1314,1 2462,6

Ut il 2 CPU 198,48% 197,18% 197,71% 197,85% 197,73% 195,55%

0,45 0,50 0,55

0,018

0,028

0,038

Ni(CO)4: Variation of 3(OC)Ni-CO

MINI

MIDI

3N21

6N316N31-dp

6N31-2d2p

TZV

TZV-dp

TZV-2d2p

Mhs-tm

Mhs-ptm

Cct

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Here is an overview of total energy of each basis set and calculation time.

MINI MIDI 3N21 6N31 6N31-dp 6N31-2d2p

Energie -1951,9668 -1952,7950 -1952,1341 -1961,3597 -1961,5631 -1961,6069

Zeit 85,9 170,1 176,5 225,7 582,6 1382,7Ut il 2 CPU 199,93% 199,29% 198,41% 198,48% 197,18% 197,71%

On previous calculations we saw that except STO-2 and MINI most basis sets are acceptable good for

H,C,O calculations. For research we should use there at least 6-31-(pd). On Ni(CO4) we see that even a

good split valence set with polarization functions have problems. So one should use for calculations

which contains transition metals at least a triple valence set.

We know calculation time hardly depends on chosen basis set, so we should look for some agreements.

Using of hybrid sets with hough sets for transition metals and smaller sets for first two row elements is

one strategy. On the other hand we create a kind of artefacts because, different sets have different

strategies in describing orbitals and we have no consequent description by using hybrids.

But every one can decide which kind of accuracy he needs.

For didactical of private usage 6-31 is acceptable, but for research one should use a least a triple

valence set.

TZV TZV-dp TZV-2d2p Mhs-tm Mhs-ptm Cct

Energie -1961,7251 -1961,9104 -1961,9254 -1961,6495 -1955,9510 -1956,1494

Zeit [s] 739,2 1314,1 2462,6 372,7 6901,0 ~1 day

Ut il 2 CPU 197,85% 197,73% 195,55% 194,56% 199,05%

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Here is another benchmark of a komplex. Cl-Mn(CO)5 streching Cl-Mn Bond

-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60

0,00

0,05

0,10

Cl-Mn(CO)5

distance to equilibrium lenght [A]

energyrelativeto

groundstateE

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Text

-0,15 -0,05 0,05 0,15 0,25 0,35 0,45 0,55 0,65 0,75 0,85

-0,05

0,00

0,06

Cl-Mn(CO)5

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

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Text

0,05 0,10 0,15

-0,004

0,001

0,006

Cl-Mn(CO)5

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

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Text

0,45 0,50 0,55

0,018

0,023

0,028

0,033

Cl-Mn(CO)5

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

b h k f O h dd l b d h d

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Here is a benchmark of Ni(CO)4 again. With additional basis sets and new hardware.

-0,10 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,30

0,000

0,050

0,100

0,150

0,200

0,250

3OCNi-CO stretch of Ni(CO)4

distance to equilibrium lenght [A]

energyrelativeto

groundstateE

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Text

-0,15 -0,05 0,05 0,15 0,25 0,35 0,45 0,55 0,65 0,75 0,85

-0,05

0,00

0,06

Ni(CO)4

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

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Text

0,05 0,10 0,15

-0,004

0,001

0,006

Ni(CO)4

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

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Text

0,45 0,50 0,55

0,018

0,023

0,028

0,033

Ni(CO)4

MINI

6N31-pd

CCD

CCT

SVP

TZVP

ptm2

ptm3

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Another important question in chemistry is the difference between some conformations.

To prove how energy difference depends on basis set we compare cis/trans conformer of but-2-ene.

Additionally we can compare calculated dipol of each conformer.

Energy Dipol Time # Iter

Cis Trans Diff Cis Trans Cis Trans Cis Trans

STO-2 -150,7977 -150,7994 0,001680 0,164597 0,000196 1,8 1,8 9 9

MINI -156,2157 -156,2168 0,001119 0,229661 0,000370 2,3 2,2 9 9

MIDI -156,3047 -156,3067 0,002003 0,179939 0,000298 4,1 3,5 9 8

3N21 -156,3717 -156,3736 0,001948 0,202529 0,000283 4,0 3,8 9 9

6N31 -157,1904 -157,1925 0,002071 0,195935 0,000281 5,6 5,0 10 9

6N31-dp -157,2370 -157,2392 0,002135 0,197658 0,000254 13,5 11,8 10 9

DZV-dp -157,2521 -157,2539 0,001797 0,228780 0,000283 16,3 14,5 11 10

6N311-2p2d -157,2812 -157,2833 0,002122 0,212560 0,000245 40,5 38,0 9 9

TZV-2p2d -157,2892 -157,2912 0,002040 0,249976 0,000247 49,9 43,5 10 9

ACCT -157,2928 -157,2949 0,002022 0,262794 0,000252 1024,6 1038,8 12 12

Here we see the same tendency that STO-2 & MINI set is significant different to split or triple zeta sets.

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Now let's assay the dipole moment of DMF. Geometry was optimized by 6-311-dp/B3LYP

Table contain energy, dipole moment, mulliken population diff. and computational time.

Dipol moment for liquid DMF is 3,86 Debye.

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Because in previous test we get some worse mulliken populations with good sets, here is another

molecule. On 4-aminobenzonitril (6-311(pd) Geometry) we test differences of basis sets.

Here we see again that there is some kind of inconsistency in describing electron density.

In some cases we have partial negatively in other partial positively charged nitrogen of nitril-group.

We would expect a partial negative charge, so here we have a good example that bigger sets don't meen

automatically better/realer descriptions.

.. to be continued

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- more benchmarks of metal-organic molecules

- benchmarks of excited states

- benchmarks of different hybrid basis sets

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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 the author.

It is literary property of Marek Pawel Checinski.

Leibniz-Institut fr Katalyse e.V.

http://www.chemie.hu-berlin.de/

http://www.catalysis.de/

mail: marek.checinski catalysis.de

http://www.chemie.hu-berlin.de/http://www.catalysis.de/mailto:marek.checinski%20catalysis.de?subject=[PC-Gamess-Tutorial]%20mailto:marek.checinski%20catalysis.de?subject=[PC-Gamess-Tutorial]%20http://www.catalysis.de/http://www.chemie.hu-berlin.de/