scholarly journals The Use of Quantum-Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part II: The Lattice Energies of α- and β-Oxalic Acid (COOH)2

2002 ◽  
Vol 57 (12) ◽  
pp. 961-966 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Oxalic Acid ◽  
Quantum Chemical ◽  
Lattice Energy ◽  
Energy Difference ◽  
Electrostatic Energy ◽  
Semiempirical Methods ◽  
Stable Form ◽  
Crystal Lattices ◽  
Lattice Energies ◽  
Chemical Procedure

The lattice energies (ΔE lat) of α- and β-oxalic acid ((COOH)2) have been calculated using a recently introduced semiempirical quantum-chemical procedure. Within the framework of this method the lattice energy (ΔE lat) is evaluated as the sum of the semiempirically calculated intermolecular dispersion (ΔEdis), induction (ΔEind), repulsion (ΔErep), and electrostatic energy (ΔEels). The lattice energies of the two polymorphs of oxalic acid obtained in this way correlate not only with the results of other calculations but also with the experimentally determined heats of sublimation in that the α-modification, which has a somewhat higher heat of sublimation, is slightly more stable than the β-polymorph. However, additional quantum-chemical calculations at the non-empirical ab initio level (e. g. ZPE+MP2(FC)/6-311++G**//MP2(FC)/6-311++G**) revealed that the absolute values of the lattice energies and the heats of sublimation are not directly comparable to each other because the structures of the (COOH)2 molecules in the crystal lattices of both polymorphs differ significantly from that of the most stable form of the free molecule in the gasphase. At about 4.3 kcal/mol the calculated energy difference between the structure of the molecule in the solid state and the energetically most favourable conformation of the free (COOH)2 molecule in the gasphase is much smaller than that in the recently described case of α-glycine (28±2 kcal/mol). However, even such a small difference might be the source of serious problems if the heats of sublimation are employed to fit parameters to be used in the optimization of crystal packings.

scholarly journals The Use of Quantum Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part I: The Three Polymorphs of Glycine

2000 ◽  
Vol 55 (6-7) ◽  
pp. 609-615 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Quantum Chemical ◽  
Chemical Method ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Potential Method ◽  
Electrostatic Energy ◽  
Semiempirical Methods ◽  
Quantum Chemical Method ◽  
Organic Molecular Crystals ◽  
Lattice Energies

Abstract A method to calculate the lattice energies of organic molecular crystals is described. It is based on the semiempirical quantum chemical MINDO/3 approximation but might also be used within the framework of any other quantum chemical method. The lattice energy is approximated by the sum of dispersion-, induction-, exchange repulsion-, and electrostatic energy. Different, however, from other schemes employed in this field, like for example the atom-atom-potential method, the variables in the expression for the lattice energy have not been fitted to reproduce experimental values and, therefore, the single contributions retain their original physical meaning. Moreover, the method offers the advantage that it may be directly applied to all compounds that can be treated within the framework of the underlying quantum chemical method. Thus, time consuming readjustment of the entire parameter set upon extension of the group of target molecules by another class of compounds becomes obsolete. As an example, the lattice energies of the three polymorphs of glycine are calculated.

scholarly journals The Use of Quantum-Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part III: The Lattice Energy of Borazine (B3N3H6) and its Packing in the Solid State*

2004 ◽  
Vol 59 (9) ◽  
pp. 609-614 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Quantum Chemical ◽  
Lattice Energy ◽  
Low Pressure ◽  
Semiempirical Methods ◽  
Dispersion Energy ◽  
Organic Molecular Crystals ◽  
Ab Initio Theory ◽  
Lower Melting Point ◽  
Chemical Scheme ◽  
Lattice Energies

A previously presented quantum-chemical scheme has been used to calculate the lattice energies of borazine (B3N3H6), the low pressure polymorph of benzene (C6H6), and of borazine in the lowpressure benzene lattice utilizing some frequently used semiempirical methods (CNDO/2, INDO, MINDO/3, MNDO, AM1, PM3, MSINDO). With all methods the lattice energy of the title compound was found to be less favourable than that of isoelectronic benzene, which offers an explanation of the significantly lower melting point of B3N3H6. Calculation of the lattice energy of borazine in the crystal lattice of the low-pressure modification of benzene revealed that the interactions between the molecules in this environment are not so stabilizing as those in its own lattice. This is predominantly due to a less favourable contribution of the dispersion energy. The semiempirical results have qualitatively been confirmed by quantum-chemical calculations on small molecular clusters at the MP2/6-31+G*//HF/6-31+G* level of ab initio theory. In these calculations we assumed pairwise additivity of the intermolecular interactions and calculated the energy of interaction between a reference molecule and all those neighbours to which the shortest intermolecular distance does not exceed 3Å.

scholarly journals A Density Functional Theory Study on Paracetamol-Oxalic Acid Co-Crystal

2020 ◽  
pp. 11-18
Author(s):  
Punya Paudel ◽  
Krishna Raj Adhikari ◽  
Kapil Adhikari
Keyword(s):  
Density Functional Theory ◽  
Oxalic Acid ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Lattice Energy ◽  
Stable Form ◽  
Functional Theory ◽  
Monoclinic Form ◽  
Hydrogen Bonded

Paracetamol (PCA) has two well-known polymorphic forms, monoclinic (form I) and orthorhombic (form II). The parallel packing of flat hydrogen bonded layers in the metastable form II results in compaction properties superior to the thermodynamic stable form I which contains corrugated hydrogen bonded layers of molecules. In this study, the structure of Paracetamol (PCA)-Oxalic acid (OXA) co-crystal has been analyzed and found layered structure similar to PCA form II which enhance ability to form tablet. The Density Functional Theory (DFT) has been conducted to find some physicochemical properties of co-crystal. It was observed that the lattice energy of co-crystal is more than that of PCA form II showing more stability on co-crystal. The energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO gap) in co-crystal was found less than PCA form II showing bigger enhancement of reactivity.

Estimation of Lattice Energies of Organic Molecular Crystals by Combination of Experimentally Determined and Quantum- Chemically Calculated Quantities: A New Value for the Lattice Energy of a-Glycine

1999 ◽  
Vol 54 (10-11) ◽  
pp. 611-616 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Total Energy ◽  
Ab Initio ◽  
Gas Phase ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Energy Difference ◽  
Crystalline Form ◽  
Stable Form ◽  
Organic Molecular Crystals ◽  
Ab Initio Theory

A new value for the lattice energy of a-glycine was determined by combination of the experimentally measured heat of sublimation taken from literature and the quantum-chemically calculated energy difference Etot,gp - Etot,cry, where Etot,gp is the total energy of the most stable form of the compound in the gas phase (carboxylic acid) and Etot,cry the total energy of the molecule as it occurs in its crystalline form (betaine). At the highest levels of ab initio theory employed in this study this energy difference is -(28±2) kcal/mol, indicating that older work overestimated this difference significantly. The reason for the overestimation of this energy difference was determined by means of additional ab initio calculations. The lattice energy of -(67±2)kcal/mol obtained using the new value for Etot,gp - Etot,cry is significantly more positive than an older value of -103 kcal/mol frequently cited in the literature.

On the reliability of volume-based thermodynamics for inorganic-organic salts and coordination compounds with uncharged ligands

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Coordination Compound ◽  
Coordination Compounds ◽  
Formation Enthalpy ◽  
Lattice Energy ◽  
Chemical Hardness ◽  
Acid Anion ◽  
Organic Salts ◽  
Density Values ◽  
Lattice Energies

In the present work, the reliability of the volume-based thermodynamics (VBT) methods in the calculation of lattice energies is investigated by applying the “traditional” Kapustinskii equation [8], as well as Glasser-Jenkins [3] and Kaya [5] equations to calculate the lattice energies for Na, K and Rb pyruvates [9-11] as well as for the coordination compound [Bi(C<sub>7</sub>H<sub>5</sub>O<sub>3</sub>)<sub>3</sub>C<sub>12</sub>H<sub>8</sub>N<sub>2</sub>] [17] (in which C<sub>12</sub>H<sub>8</sub>N<sub>2</sub> = 1,10 phenathroline and C<sub>7</sub>H<sub>5</sub>O<sub>3</sub><sup>-</sup>= <i>o</i>-hyddroxybenzoic acid anion). As comparison, the lattice energies are also calculated using formation enthalpy values for sodium pyrivate and [Bi(C<sub>7</sub>H<sub>5</sub>O<sub>3</sub>)<sub>3</sub>C<sub>12</sub>H<sub>8</sub>N<sub>2</sub>]. For the pyruvates, is verified that none of the considered approach, Kapustinskii, Glasser, Kaya or density, provides values that agrees in an acceptable % difference, with the lattice energy values calculated from the formation enthalpy values. However, it must be pointed out that Kaya approach, with deals with a chemical hardness approach is the better one for such kind of inorganic-organic salts. Based on data obtained for [Bi(C<sub>7</sub>H<sub>5</sub>O<sub>3</sub>)<sub>3</sub>C<sub>12</sub>H<sub>8</sub>N<sub>2</sub>] is concluded that the only one VBT method that provides reliable lattice energies for compounds with bulky uncharged ligands is that one based on density values (derived by Glasser-Jenkins).

scholarly journals The Face-to-Face σ-Hole···σ-Hole Stacking Interactions: Structures, Energies, and Nature

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 877
Author(s):  
Yu Zhang ◽  
Weizhou Wang
Keyword(s):  
Quantum Chemical ◽  
Noncovalent Interactions ◽  
Electrostatic Energy ◽  
Stacking Interactions ◽  
Energy Component ◽  
Stacking Interaction ◽  
Face To Face ◽  
The Face ◽  
Π Stacking Interaction ◽  
Induction Energy

The existence of the π···π stacking interaction is well-known. Similarly, it is reasonable to assume the existence of the σ-hole···σ-hole stacking interaction. In this work, the structures, energies, and nature of the face-to-face σ-hole···σ-hole stacking interactions in the crystal structures have been investigated in detail by the quantum chemical calculations. The calculated results clearly show that the face-to-face σ-hole···σ-hole stacking interactions exist and have unique properties, although their strengths are not very significant. The energy component analysis reveals that, unlike many other dispersion-dominated noncovalent interactions in which the induction energies always play minor roles for their stabilities, for the face-to-face σ-hole···σ-hole stacking interaction the contribution of the induction energy to the total attractive energy is close to or even larger than that of the electrostatic energy. The structures, energies, and nature of the face-to-face σ-hole···σ-hole stacking interactions confined in small spaces have also been theoretically simulated. One of the important findings is that encapsulation of the complex bound by the face-to-face σ-hole···σ-hole stacking interaction can tune the electronic properties of the container.

A new approach to the calculation of electrostatic energy relations in minerals: the dioctahedral and trioctahedral phyllosillicates

1979 ◽  
Vol 293 (1401) ◽  
pp. 169-208 ◽  
Keyword(s):  
Computer Time ◽  
Quadratic Functions ◽  
Electrostatic Energy ◽  
Complex Structures ◽  
X Ray Diffraction ◽  
New Approach ◽  
Considerable Saving ◽  
Lattice Energies ◽  
Energy Relations ◽  
Made In

This paper presents an original and useful method for calculating and comparing the electrostatic component of the lattice energies of families of related, complex structures. The methodology and use of hypothetical, tractable steps in passing from one structure to another can be extended to families of crystal structures other than the phyllosilicates. Calculations made on a single ‘generic’ silicate, KX 2 X'T 4 O 10 (OH) 2 , enables us to obtain the lattice energies of 1M aluminium mica, phlogopite, talc, pyrophyllite, saponite, beidellite, illite, montmorillonite and hectorite and their fluorinated analogues. Site potentials are readily obtained when calculations are made in this manner. Considerable saving of computer time and effort coupled with little sacrifice of accuracy are a feature of this approach. The paper further goes on to suggest how comparison of this type of generic calculation with the results obtained from calculations made on the true individual phyllosilicate structure can extend the potential information that can be gained from these studies. The investigation of substitutional and relaxation energies of the phyllosilicates is considered. Surface energies (shown to be quadratic functions of x for micas derived from the structure A X X 2 X'T 4 O 10 (OH) 2 , (A = Na or K)) are calculated on the same principle, from, in this case, a ‘generic’ expanded lattice. The transferability principle introduced in this work enables us to make specific predictions regarding minerals for which single crystal X-ray diffraction studies are impractical. We attempt wherever possible an interpretation of the energies we calculate.

scholarly journals Simulation of thermal reaction mechanism between energetic components of hydroxyl-terminated polybutadiene propellant based on quantum chemical calculation

2019 ◽  
Vol 44 (4) ◽  
pp. 324-335
Author(s):  
Huang Weijia ◽  
Minghua Chen ◽  
Zhentao An ◽  
Li Zhang ◽  
Zhibao Jiang
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Quantum Chemical ◽  
Closed Shell ◽  
Energy Difference ◽  
Thermal Reaction ◽  
Chemical Calculation ◽  
Shell Layer ◽  
Hybrid Functional ◽  
B3lyp Method

In this article, hybrid functional B3LYP method is used to construct the reactant structure of energetic components in propellant at the bhandhlyp/6-31g(d) level, and to calculate the closed-shell layer of the system. At the bhandhlyp/6-31g(d) level, the energy difference (activation energy) between the transition state and the reactant was calculated and the reaction mechanism between energetic components was analyzed. It is found that the O30 atom of RDX first breaks off from the nitro group and is easier to break away from RDX and interact with the vertex atom Al1 of the Al13 cluster. With the further separation of O30, it also acts with Al11 until it completely breaks away from N26 atom. The activation energy of this reaction is 56.448 × 103 J mol−1. The oxygen dioxide atom in ammonium perchlorate is more likely to interact with the Al11 atom of the Al13 cluster. With the reaction proceeding, the O22 atom will not completely separate from the Cl19 atom. The activation energy of the reaction is 27.830 × 103 J mol−1.

Sign in / Sign up

Export Citation Format

Share Document