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BLW method & HuLiS program

To the Tutors

Sason remarks and prospective 2 hours talk +

Philippe's remark on the initially proposed tutorial. are included in bold.

Qualitative

• ?...

Computational

Proposal from Yirong

1. benzene and formamide - focus is on the structural and energetic impact from conjugation, and how to correlate the results with experimental evidences;
2. butadiene - focus is on the conjugation in the planar structure and the hyperconjugation in the staggered structure, and their impact on the rotational barrier;
3. acid-base and H-bonding systems: BLW energy decomposition analyses.
4. visualize the results. I have been using GaussView and ChemDraw, but other graphical software should be fine with me as well.
5. Questions from any participant can be discussed and tested on site.

Exercices

Exercice 1 (Lewis structures, of benzene, resonance)

Subject

Exercise 1: Benzene

The benzene molecule is commonly represented as the resonance between the two Kékulé structures. The aim of the exercise is to understand the relative importance of the different Lewis structures in the benzene molecule using BLW and [[1]].

According to IUPAC’s Goldbook, resonance energy is defined as “The difference in potential energy between the actual molecular entity and the contributing structure of lowest potential energy”. However this definition does not precise what is the geometry of the contributing structure of lowest potential energy. Consequently, we can define two type of resonance energy: the vertical resonance energy (VRE) and the adiabatic resonance energy (ARE).

To do

1 - With the BLW program, optimize the benzene molecule and the hypothetical 1,3,5-cyclohexadiene.: - Compare the C-C bond distances. Comment. - Calculate the VRE - Optimize the structures to get the ARE. Comment. - Compare the resonance energy computed by the BLW method and the conventional experimental resonance energy based on the hydrogenation heats of benzene and cyclohexene.

$CONTRL ICHARG=0 SCFTYP=RHF RUNTYP=OPTIMIZE $END
$DFT DFTTYP=B3LYP $END

! $BLW NBLOCK=4 ITER=80 $END

$SCF DIRSCF=.FALSE.  FDIFF=.FALSE. $END
$SYSTEM TIMLIM=600000 MEMORY=10000000 $END
$basis  gbasis=n311 ngauss=6 npfunc=1 ndfunc=1 DIFFSP=.true. $end

!$BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 $END

$GUESS  GUESS=HUCKEL $END

 $DATA
 B3LYP/6-311+G* optimized geometry
 C1  1
 C           6.0   0.0000006339   0.0000000000   1.3947932255
 C           6.0   1.2082299733   0.0000000000   0.6973544513
 C           6.0   1.2082233942   0.0000000000  -0.6973491014
 C           6.0   0.0000000658   0.0000000000  -1.3948010538
 C           6.0  -1.2082223644   0.0000000000  -0.6973489478
 C           6.0  -1.2082278726   0.0000000000   0.6973527321
 H           1.0  -0.0000049345   0.0000000000   2.4799156106
 H           1.0   2.1470883835   0.0000000000   1.2408733122
 H           1.0   2.1470838307   0.0000000000  -1.2408743510
 H           1.0  -0.0000002627   0.0000000000  -2.4799186833
 H           1.0  -2.1470846317   0.0000000000  -1.2408715385
 H           1.0  -2.1470862154   0.0000000000   1.2408743441
 $END

2 – With the hulis program: - Draw the benzene and create then the two kékulés structures - Add to the wave function the 3 covalent Dewar structures

Stéphane could you complete this part to add questions about the completude de base.

Access to files :

allyl.bfi, .xmi and orb

butadiene.xmi

Exercice 4 (BH3... NH3) electronics at the B3LYP 6-31G(d) level

BLW energy decomposition analysis can be used to shed light into the nature of intermolecular interactions. Example of NH3∙∙∙BH3. Visualize the polarization and electron transfer effects using the electron density difference (EDD) maps.

1/ Make orbitals of BH3 alone (then NH3) in the geometry of the complex

 $DATA
 BLW-ED Analysis
 C1  
 N   7.0        0.000000    0.000000    0.728869
 H   1.0        0.000000    0.951707    1.095972
 H   1.0        0.824202   -0.475853    1.095972
 H   1.0       -0.824202   -0.475853    1.095972
 B   5.0        0.000000    0.000000   -0.934793
 H   1.0        0.000000   -1.170908   -1.238679
 H   1.0       -1.014036    0.585454   -1.238679
 H   1.0        1.014036    0.585454   -1.238679 
 $END

2/ Let fragment orbitals to polarize in the full complex.

3/ Let delocalize. This is just a standard DFT calculation. (TO CHECK with Yirong)

Preliminary Remarks : B3LYP calculation in Gamess is specified in $CONTRL :

 $CONTRL SCFTYP=RHF DFTTYP=B3LYP runtyp=energy maxit=200 icharg=0 $END

And 6-31G(d) basis set is requested with

  $BASIS  GBASIS=N31 NGAUSS=6 NDFUNC=1 $END

Step by step help :

1/ Perform a NH3 BLW calculation of the fragment alone in the geometry of the complexe with $BLW NBLOCK=1 and keep the .blw file for next step (same for BH3).

We obtain

nh3.log: FINAL R-B3LYP ENERGY IS -56.5111505350

bh3.log: FINAL R-B3LYP ENERGY IS -26.5644674370

= > summ = -83.07561797

2/ Do the complex in a NBLOCK=2 BLW calculation and see the polarization of each fragment. The initial orbitals are obtained from .blw files of individual fragments ---ORBITALS (LOCAL BFS)--- part, and copied after the $BLWDAT fragments definition. A blank line separate each fragments’guess.

At this stage, we can want to do the calculation at full accuracy from the very first step. The following line avoid initial SCF cycles (SWOFF=0.0), and initial coarse grid DFT steps :

 $DFT SWOFF=0.0 NRAD0=96 NLEB0=302 NTHE0=12 NPHI0=24 $END

We obtain

ITER 1 E(RBLW) = -83.05921870

FINAL R-B3LYP ENERGY IS -83.0932178520

3/ We let just the doublet to delocalize. TO CHECK with Yirong

We obtain

FINAL R-B3LYP ENERGY IS -83.1480131227 AFTER 12 ITERATIONS

all input files are there