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2018
Adsorption of Titanium Tetrachloride on Magnesium Dichloride Clusters
Zorve, Peter
American Chemical Society (ACS)
Tieteelliset aikakauslehtiartikkelit
© American Chemical Society ACS AuthorChoice
http://dx.doi.org/10.1021/acsomega.8b01878
https://erepo.uef.fi/handle/123456789/6981
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Adsorption of Titanium Tetrachloride on Magnesium Dichloride Clusters
Peter Zorve and Mikko Linnolahti*
Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
*S Supporting Information
ABSTRACT: Magnesium dichloride and titanium tetrachlor- ide are key components in heterogeneous Ziegler−Natta olefin polymerization catalysis. We have determined the preferred binding modes of titanium tetrachloride on magnesium dichloride clusters at the M06-2X level of theory, thus accounting for dispersion. A systematic study was carried out to locate the lowest energy isomers of (MgCl2)n(TiCl4)m complexes. Altogether ca. 1000 complexes with n ranging from 1 to 19 andmfrom 1 to 13 were studied. In line with the previous literature, the results consistently show that adsorption of TiCl4onto MgCl2preferably leads to octahedral
six-coordination for both Mg and Ti atoms. This can be achieved by mononuclear binding of TiCl4and binuclear binding of Ti2Cl8 on (110) and (104) surfaces of MgCl2, respectively. The preferred octahedral six-coordination is also achieved by binding of TiCl4on defect sites, of which the most striking example is trinuclear binding mode at corners of the clusters.
Overall, the results highlight the relevance of multinuclear binding of TiCl4on MgCl2.
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INTRODUCTIONHeterogeneous Ziegler−Natta (ZN) catalysis is currently the main technique for industrial production of polyolefins.1,2The current state-of-the-art ZN catalysts are composed of MgCl2, TiCl4, and a Lewis base (internal donor).3 Contacting the ternary mixture with a trialkyl aluminum cocatalyst and another and Lewis base (external donor) yields the catalytically active species with reduced oxidation states of Ti.2,4 Each of these components play a significant role in the polymerization process, though their precise functions are not fully understood and the structure of the catalyst is ill-defined because of a high complexity of the overall system.1−3
The catalytic reactions take place on the surfaces of the MgCl2 support.5,6 The bulk MgCl2 is a crystalline layered material, which exists in three polymorphs: rhombohedralα- MgCl2, hexagonally closed-packed β-MgCl2, and rotationally distortedδ-MgCl2. The layers are held together by dispersion and are composed of octahedral six-coordinated Mg atoms bound to three-coordinate Cl atoms (Figure 1A).7−10Lateral cut of the MgCl2 sheets exposes catalytically relevant (104) and (110) surfaces with five- and four-coordinate Mg atoms, respectively (Figure 1B),11which adsorb and coadsorb TiCl4, aluminum alkyls, and Lewis bases.12−20 The (110) surface is less stable than the (104) surface because of the lower coordination numbers of surface Mg atoms,18,19,21 but adsorption of other catalyst components may reverse the stability order in favor of (110).22,23Reactions taking place on the surface eventually lead to the formation of active sites for olefin polymerization.7,19,24−29
Little is known about the reactions at atomic-level detail;
there is not even consensus on how TiCl4 adsorbs on the MgCl2support in the absence of other catalyst components.
The binding modes have been widely studied by quantum chemical calculations, though, with varying results and conclusions.10,11,30−36 Four commonly discussed binding modes are illustrated in Figure 1C. Adopting a previously defined naming convention, which specifies the coordination number of Ti followed by the MgCl2surface, these are4-110, 5-104, 6-110, and 6-104.7 In addition, 5-110 mode has been proposed but later questioned.11,37Spectroscopic experiments indicate octahedral six-coordination of Ti atoms,21,38 which also rules out the4-110 and 5-104 modes. Alongside with6- 110 and6-104, defects on the surfaces generate environments allowing for the octahedral six-coordination.36,39−43
Octahedral six-coordination of Ti has been widely considered to signal mononuclear 6-110 binding or mono- nuclear binding on a defect site of MgCl2.40The mononuclear binding is generally concluded to be favored over binuclear octahedral6-104 binding based on the weaker binding energy of the latter. However, as has been shown recently, this is a biased conclusion, omitting the higher reactivity of the (110) surface.7In a systematic computational study reported herein, we determine the preferred binding modes of TiCl4 on selected (MgCl2)n clusters up to n = 19 based on thermodynamic stabilities of the products rather than binding
Received: August 3, 2018 Accepted: August 14, 2018 Published: August 24, 2018
Article http://pubs.acs.org/journal/acsodf Cite This:ACS Omega2018, 3, 9921−9928
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energies. As it turns out, multinuclear binding modes of TiCl4 are highly relevant on the (104) surface and possibly on defect sites of MgCl2as well.
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RESULTS AND DISCUSSIONBinding of TiCl4 on (MgCl2)n Clusters (n = 1−4). We begin by a systematic and thorough exploration of the binding of TiCl4 on (MgCl2)n, where n = 1−4, to form (MgCl2)n− (TiCl4)m complexes. The (MgCl2)n clusters were obtained from a previous work by Luhtanen, et al.8Here and in all that follows, all theoretically possible structures were initially constructed for each cluster followed by structure optimization.
This resulted in optimization of 31 (MgCl2)−(TiCl4)m complexes, where m = 1−5, 63 (MgCl2)2−(TiCl4)m com- plexes, where m= 1−6, 144 (MgCl2)3−(TiCl4)m complexes, where m = 1−8, and 303 (MgCl2)4−(TiCl4)m complexes, wherem= 1−8.
The located lowest energy structure of each combination of nandmis shown inFigure 2. We use the nomenclature (n,m) to specify the number of MgCl2(n) and TiCl4(m) units in the presentation and discussion of the results. The driving force for the reactions is the tendency of both Mg and Ti to attain octahedral six-coordination. In the case of monomeric MgCl2, this is achieved for Mg, as well as for each Ti, upon binding of five TiCl4 molecules (1,5), thus leaving no further reactive sites. The (MgCl2)2dimer attains octahedral six-coordination for the Mg atoms at (2,6), the trimer at (3,8), and the tetramer at (4,6).
Electronic energies and Gibbs energies for the reaction (MgCl2)n+ (TiCl4)m→(MgCl2)n−(TiCl4)mcalculated by the M06-2X/TZVP method44,45 are given in Table 1. Energies
improve along gradual saturation of the (MgCl2)nclusters by the TiCl4 molecules. However, Gibbs energies show that entropy plays a major role in the process, preventing full saturation of the small clusters. For the monomer, dimer, and trimer, the minimum in Gibbs energy was found at m = 2, resulting in chain structures with four-coordinate magnesiums, terminated by five-coordinate titaniums at each end. The tetramer shows a distinctly different behavior. It finds the minimum in Gibbs energy atm= 6, where each Mg atom and four out of six Ti atoms obtain octahedral six-coordination in resemblance to the basal MgCl2surface.
To demonstrate the importance of dispersion in arriving at these conclusions, we report the reaction Gibbs energies in Table 1 also by the popular PBE0 method46,47 lacking description for dispersive interactions. In line with previous studies,7,48 PBE0 predicts much weaker binding between magnesium dichloride and titanium tetrachloride, particularly at large values ofm. Consequently, the PBE0 method ends up favoring the (4,2) structure for the tetramer with two four- coordinate magnesiums, in resemblance to the (110) surface of MgCl2.
Binding of TiCl4 on (MgCl2)7.On the basis of the above results, considering dispersion by the M06-2X method, one could also envisage that MgCl2 clusters larger than the tetramer favor full coverage by TiCl4to obtain octahedral six- coordination for Mg, which is also possible for the Ti atoms.
Wefirst show that this is the case for the (MgCl2)7heptamer, Figure 1. (A) Structure of the MgCl2 layer, (B) (110) and (104)
surfaces, and (C) binding modes of TiCl4. Mg, Cl, and Ti atoms are shown in yellow, green, and white, respectively.
Figure 2.Optimized lowest energy structures of (MgCl2)n−(TiCl4)m, wheren= 1−4 andm = 1−8. Mg, Cl, and Ti atoms are shown in yellow, green, and white, respectively.
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which is the simplest hexagonal structure with one saturated octahedral magnesium and six unsaturated surface magne- siums. The latter are the reactive sites, two of them havingfive- coordination and four four-coordination, similar to the (104) and (110) MgCl2surfaces, respectively.
Altogether 141 (7,m) complexes, where m = 1−9, were optimized. The located lowest energy structure of each combination of n and m is shown inFigure 3 with energies and Gibbs energies for the reaction (MgCl2)7 + (TiCl4)m → (MgCl2)7−(TiCl4)m given in Table 2. The calculated Gibbs energies show that the reactions are much more exergonic for the heptamer than for the monomer to the tetramer discussed above. Thefirst TiCl4molecule makes a bidentate binding to the more reactive four-coordinate surface magnesiums, and upon reaction of three TiCl4molecules, all surface magnesiums reach five-coordination. The reaction continues further until each magnesium attains octahedral six-coordination, which is reached atm= 7. However, because of the preference of also titanium for attaining octahedral six-coordination, the reaction continues further until (7,8), where the six-coordination of each Ti is obtained by trinuclear binding of TiCl4. We are not aware of any previous reports of trinuclear TiCl4 on MgCl2, possibly because the calculations have typically dealt with idealized (104) and (110) MgCl2 surfaces. Formation at a corner suggests that the trinuclear binding mode may be relevant at defect sites of the MgCl2surface.
Extension to Larger (MgCl2)nClusters (n= 14, 19).As afirst step to evaluate how the above results on small MgCl2 clusters translate to MgCl2 surfaces, we turn the attention to two isomers of (MgCl2)14, which are adopted from a previous work, including their namings.23 The pipe and diamond
isomers of (MgCl2)14provide simplified models for the (110) and (104) surfaces of MgCl2, respectively (Figure 4top). Both models contain 4 octahedral six-coordinated Mg atoms that do not participate in reaction with TiCl4and 10 reactive surface Mg atoms, of which 6 are four-coordinate and 4 are five- coordinate in the pipe model, whereas 6 are five-coordinate and 4 are four-coordinate in the diamond model. The pipe isomer is 23.0 kJ mol−1 lower in energy, indicating that the adjacent five-coordinate magnesiums introduce certain strain to the diamond isomer because of its small size. For comparison, we, therefore, also include a larger model for the representation of the (104) surfaces, hexagonal (MgCl2)19 Table 1. Energies and Gibbs Energies (kJ mol−1) for the
Reaction (MgCl2)n+ (TiCl4)m→(MgCl2)n−(TiCl4)m
n m ΔrE/M06-2X ΔrG/M06-2X ΔrG/PBE0
1 1 −73.6 −32.4 −18.0
1 2 −153.8 −64.8 −34.4
1 3 −186.5 −44.8 −7.9
1 4 −259.5 −30.4 94.8
1 5 −315.7 −24.2 144.4
2 1 −82.2 −32.3 −17.1
2 2 −163.6 −66.3 −33.3
2 3 −196.8 −50.1 −7.6
2 4 −273.1 −39.9 79.0
2 5 −323.0 −27.6 133.3
2 6 −363.9 −9.3 169.9
3 1 −81.3 −33.4 −16.4
3 2 −162.4 −67.0 −32.9
3 3 −195.7 −46.9 −7.0
3 4 −268.0 −38.4 83.1
3 5 −316.6 −32.2 108.1
3 6 −361.6 −9.5 189.0
3 7 −436.8 −6.7 257.1
3 8 −492.2 −0.3 309.3
4 1 −75.1 −24.3 −7.7
4 2 −147.0 −51.2 −16.1
4 3 −231.0 −58.9 30.0
4 4 −311.9 −71.2 73.1
4 5 −342.0 −78.3 102.0
4 6 −450.2 −87.8 138.8
4 7 −497.2 −79.1 177.5
4 8 −542.1 −65.2 221.5
Figure 3.Optimized lowest energy structures of (MgCl2)7−(TiCl4)m, wherem= 1−9. Mg, Cl, and Ti atoms are shown in yellow, green, and white, respectively.
Table 2. Energies and Gibbs Energies (kJ mol−1) for the Reaction (MgCl2)7+ (TiCl4)m→(MgCl2)7−(TiCl4)m
m ΔrE/M06-2X ΔrG/M06-2X
1 −131.3 −65.7
2 −264.0 −139.8
3 −336.8 −161.2
4 −409.4 −172.9
5 −478.8 −185.2
6 −566.9 −196.7
7 −635.9 −203.6
8 −723.8 −217.3
9 −729.3 −182.8
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cluster, which has 7 octahedral six-coordinated magnesiums and 12 reactive surface magnesiums, of which 8 are five- coordinate (Figure 5 top). The (MgCl2)19 cluster is 12.2 kJ mol−1 per MgCl2 unit lower in energy than the diamond isomer of (MgCl2)14, indicating reduced strain, and 10.6 kJ mol−1per MgCl2unit lower in energy than the pipe isomer of (MgCl2)14 because of the higher average coordination numbers.
Because of thousands of possible configurations for TiCl4 binding on these larger clusters, we limit the number of bound TiCl4 molecules to the domain of full saturation of surfaces, that is,m= 8−11 for (MgCl2)14andm= 10−13 for (MgCl2)19. This narrows down the studied (14,m) complexes to 204 and (19,m) complexes to 147. The located lowest energy structures are illustrated in Figures 4 and 5 with energies and Gibbs energies for the reaction (MgCl2)n+ (TiCl4)m→(MgCl2)n− (TiCl4)mgiven in Table 3.
In each case, TiCl4adsorption continues until all magnesium atoms have reached octahedral six-coordination, which takes place atm= 10 andm= 12 forn= 14 andn= 19, respectively.
Comparison of pipe and diamond isomers ofn= 14 shows that the latter binds TiCl4much more strongly (−337.9 kJ mol−1vs
−234.7 kJ mol−1). One could argue that this is because the pipe isomer is more stable and hence less reactive than the diamond isomer, but the stability difference is only a minor contribution as is revealed by comparison of the (14,10)
isomers (Figure 6), where the diamond isomer is favored by 84.4 kJ mol−1in Gibbs energy.
Five binding modes of TiCl4can be identified for the two isomers of (14,10), as illustrated in Figure 6. Mononuclear binding on the (110) surface (A) and binuclear binding on the (104) surface (B) are the dominant binding modes resulting in the preferred octahedral six-coordination of the Ti atoms. The pipe isomer features a mononuclear binding modeC, which is analogous to the5-104 binding mode (Figure 1C). Yet another binding mode (D) is found at a corner resembling defect site.
With two bridging chlorides, D is analogous to the 4-110 Figure 4. Optimized lowest energy structures of (MgCl2)14−
(TiCl4)m, wherem = 8−11, for pipe and diamond models. Mg, Cl, and Ti atoms are shown in yellow, green, and white, respectively.
Figure 5. Optimized lowest energy structures of (MgCl2)19− (TiCl4)m, where m = 10−13. Mg, Cl, and Ti atoms are shown in yellow, green, and white, respectively.
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binding mode but is stabilized by the extra terminal Cl at the corner of the pristine (MgCl2)14 cluster, thus reaching five- coordination. Similarly, in the diamond isomer, the terminal Cl increases the coordination number of the mononuclear TiCl4 at the defect site from five to six (E), ending up with the optimal octahedral six-coordination for each titanium. Note that E is analogous to 5-104 on the ideal (104) surface.
Octahedral six-coordination is the primary reason for the diamond isomer of (14,10) being thermodynamically favored over the pipe isomer.
Moving ton= 19, the minimum in Gibbs energy is located at (19,12) with octahedral six-coordination of each magne- sium. Adsorption of 12 TiCl4molecules to saturaten= 19 is less exergonic than the adsorption of 10 TiCl4 molecules to
saturate the diamond isomer ofn= 14 (Table 3). AsFigure 7 illustrates, (19,12) cannot attain the optimal octahedral six-
coordination for each Ti because it would lead to a wrong overall stoichiometry. Consequently, two of the adsorbed TiCl4 molecules are forced to adopt monodentate binding of TiCl4, leading to unfavorable four-coordinate surface titaniums.
Figure 8summarizes the relevant binding modes of TiCl4on MgCl2 based on this work. The primary binding modes on pristine (110) and (104) surfaces are mononuclear A and binuclear B, respectively, both binding modes providing Ti atoms with octahedral six-coordination closely resembling the structure of the basal MgCl2layer. Octahedral six-coordination is also attained by trinuclear binding of TiCl4at a corner site having four-coordinate Mg and by mononuclear binding on a (104) surface site having an extra terminal Cl. Other binding modes (C,D, andF) can only be present at environments not allowing for octahedral six-coordination because of the immediate surroundings.
The calculated reaction Gibbs energy (−337.9 kJ mol−1, Table 3) to form the diamond isomer of (14,10), which features octahedral six-coordination of each Ti with domi- nation of the binuclear binding mode (B), corresponds to average adsorption Gibbs energy of−33.8 kJ mol−1per TiCl4. For (19,12), the average adsorption Gibbs energy decreases to
−26.3 kJ mol−1 per TiCl4. The drop is contributed by two factors as follows: (1) the presence of unsaturated Ti in (19,12) and (2) higher strain and hence higher reactivity of (MgCl2)14. A logical assumption from the latter factor is that beyondn= 19, adsorption Gibbs energies per TiCl4continue Table 3. Energies and Gibbs Energies (kJ mol−1) for the
Reaction (MgCl2)n+ (TiCl4)m→(MgCl2)n−(TiCl4)m, Wheren = 14, 19
n m ΔrE/M06-2X ΔrG/M06-2X ΔrG-c/M06-2Xa
14 pipe 8 −656.7 −215.4 −350.4
14 pipe 9 −772.4 −232.7 −401.8
14 pipe 10 −845.1 −234.7 −425.3
14 pipe 11 −845.6 −185.5 −389.3
14 diamond 8 −804.1 −287.3 −447.2
14 diamond 9 −873.3 −305.4 −481.0
14 diamond 10 −980.9 −337.9 −538.8
14 diamond 11 −965.2 −285.9 −495.2
19 10 −919.1 −289.8 −484.6
19 11 −983.8 −299.9 −511.3
19 12 −1049.4 −315.0 −541.5
19 13 −1026.1 −244.0 −486.2
aCorrection to condensed phase by multiplication of theTΔSterm by 2/3.
Figure 6.Comparison of pipe (top) and diamond (bottom) isomers of (MgCl2)14−(TiCl4)10with labeling of the (104) and (110) surfaces and identification of the binding modes of TiCl4(A−E).
Figure 7. Top: (MgCl2)19−(TiCl4)12 with identification of the binding modes of TiCl4. Bottom: Removal of the two terminal chlorines from (MgCl2)19yields optimal binding modes of TiCl4for each site but has a wrong overall stoichiometry.
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decreasing as a function of n. The assumption can be confirmed by comparison to a previous study employing infinitely large periodic models, where the calculations have been carried out at the same level of theory (M06-2X/TZVP) and where, though, the TZVP basis set was slightly different because it was optimized for periodic calculations.7 Full coverage of the infinite pristine (104) surface by binuclear TiCl4 adsorption (6-104) gives adsorption Gibbs energy of
−16.0 kJ mol−1per TiCl4, which is roughly the value toward which the (n,m) clusters dominant in the (104) surface converge as a function ofn. Further, to provide an estimate for the Gibbs energies of the reaction at condensed phase, we use a procedure, justified and employed previously, of multi- plication of the TΔS term by 2/3 to correct for solvation entropy.49−53 The results are given in the right column of Table 3(ΔrG-c/M06-2X). The correction does not affect the preferred (n,m) configuration, but it systematically increases the strength of TiCl4adsorptionon average by 19 kJ mol−1 per TiCl4.
A further question of interest is if TiCl4binds strong enough to cut the growth of MgCl2and thus affect the preferred size of the (n,m) clusters. In this regard,n= 7 versusn= 14 provides a useful comparison. The en ergy of the reaction (MgCl2)7(TiCl4)8+ (MgCl2)7(TiCl4)8→(MgCl2)14(TiCl4)10 (diamond) + 6TiCl4is 14.5 kJ mol−1, thus favoring (7,8) over (14,10). However, entropy reverses the reaction clearly in favor of (14,10) with ΔrG = −274.0 kJ mol−1 (or ΔrG-c =
−187.3 kJ mol−1 with the above correction for solvation entropy). An alternative way to shed light on this is to consider n/m= 1:1 stoichiometric compositions as a function of size (Table 4). The stabilities continue improving as a function of
size, indicating that the adsorption of TiCl4 is not strong enough to affect the growth of MgCl2crystallites.
The same conclusion can be drawn from infinitely large periodic models based on previous work, where both 6-104 and 6-110 surfaces lie above the fully saturated basal MgCl2 layer in Gibbs energy (but not in electronic energy),7and thus, thermodynamics prefers MgCl2to grow in any direction rather than adsorbed TiCl4 cutting the growth. The situation becomes markedly different in the presence of internal donors, which can bind MgCl2much stronger and which can hence be used for controlling the shape and size of the (MgCl2)n− adsorbate complexes.54,55
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CONCLUSIONSUsing the M06-2X/TZVP method and thus accounting for dispersion, we have carried out a systematic computational study on (MgCl2)n(TiCl4)mclusters (n= 1−19,m= 1−13) to locate the lowest energy structures of the clusters as a function ofnandmand to determine the preferred binding modes of titanium tetrachloride on magnesium dichloride.
With the exception of the smallest (MgCl2)nclusters (n= 1−3), (TiCl4)madsorbs on (MgCl2)nin such a way that each Mg atom attains octahedral six-coordination, which is in line with previous experiments and computations. Optimally, the adsorption simultaneously results in octahedral six-coordina- tion of each Ti atom so that the (MgCl2)n(TiCl4)m clusters resemble the basal MgCl2 surface. However, the optimal scenario is not always possible because of the immediate surroundings of the adsorption site and stoichiometric requirements, leading to coordination numbers of less than six under such circumstances.
The results indicate that multinuclear binding modes of TiCl4are more relevant than those that have been considered previously. This becomes evident from the overall structural characteristics of the lowest energy (MgCl2)n(TiCl4)mclusters, which are abundant in binuclear binding mode on sites resembling the (104) surface and even feature trinuclear binding mode at a corner resembling defect site. The preference for multinuclear binding is further supported by comparison of the relative stabilities of isomers featuring different sites.
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THEORETICAL METHODSAll structures were fully optimized by the M06-2X metahybrid GGA functional of the Minnesota 06 series,44in combination Figure 8.Relevant binding modes of TiCl4on MgCl2.AandBare
mononuclear and binuclear binding on the pristine (110) and (104) surfaces, respectively.Eis a bidentate TiCl4binding resulting in the optimal six-coordination of Ti.C, D, andF are TiCl4 bindings at MgCl2environments that do not allow octahedral six-coordination of Ti.
Table 4. Relative Stabilities (ΔG/n, kJ mol−1) of (MgCl2)n− (TiCl4)mProducts Formed fromn/m= 1:1 Stoichiometry of the Reactants
n reaction ΔG/n
1 MgCl2+ TiCl4→(MgCl2)−(TiCl4) 137.6 2 (MgCl2)2+ (TiCl4)2→(MgCl2)2−(TiCl4)2 66.5 3 (MgCl2)3+ (TiCl4)3→(MgCl2)3−(TiCl4)2+ TiCl4 53.7 4 (MgCl2)4+ (TiCl4)4→(MgCl2)4−(TiCl4)4 45.1 7 (MgCl2)7+ (TiCl4)7→(MgCl2)7−(TiCl4)7 24.2 14 pipe (MgCl2)14+ (TiCl4)14→(MgCl2)14−(TiCl4)10+
4TiCl4
8.7 14 diamond (MgCl2)14+ (TiCl4)14→(MgCl2)14−(TiCl4)10+
4TiCl4
2.7 19 (MgCl2)19+ (TiCl4)19→(MgCl2)19−(TiCl4)12+
7TiCl4
0.0
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with TZVP basis set by Ahlrichs and coworkers.45 The M06 functionals have turned out as the method of choice for systems involving dispersive interactions arising from metals bridged by halide and alkyl groups,48,56−58 and we have previously used the method for describing MgCl2- and TiCl4- containing systems analogous to the systems reported here.7,59,60 Vibrational frequencies were calculated by the harmonic approximation to verify the structures as true minima in the potential energy surface and to obtain Gibbs energies, which were calculated atT= 298 K andp= 1 atm. Condensed phase Gibbs energies were estimated from the reported gas- phase calculations by multiplication of theTΔSterm ofG=H
− TΔS by 2/3 as suggested and employed in the previous literature.49−53 All calculations were carried out by Gaussian 09.61
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ASSOCIATED CONTENT*S Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsome- ga.8b01878.
Absolute values of electronic energies, enthalpies, entropies, and Gibbs energies together with Cartesian coordinates of the reported structures (PDF)
(XYZ)
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AUTHOR INFORMATION Corresponding Author*E-mail:mikko.linnolahti@uef.fi. Phone: +358505926855.
ORCID
Mikko Linnolahti: 0000-0003-0056-2698 Notes
The authors declare no competingfinancial interest.
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ACKNOWLEDGMENTSThe computations were made possible by use of the Finnish Grid Infrastructure and Finnish Grid and Cloud Infrastructure resources (urn:nbn:fi:research-infras-2016072533).
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DOI:10.1021/acsomega.8b01878 ACS Omega2018, 3, 9921−9928 9928
