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Hu T, Chen L, Mao W. Atomistic modeling of flexoelectricity in amorphous polymers. J Mol Graph Model 2019; 92:147-153. [PMID: 31374464 DOI: 10.1016/j.jmgm.2019.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 07/05/2019] [Accepted: 07/15/2019] [Indexed: 11/25/2022]
Abstract
In this paper, the amorphous PVDF (Polyvinylidene Fluoride) and PE (Polyethylene) models are established. The relationship between configuration density and temperature is calculated by molecular dynamics simulation. The rationality of model is determined by comparing with the experimentally determined glass transition temperature Tg. Secondly, the strain gradient is applied to the main chain carbon atoms of the amorphous PVDF and PE equilibrium configuration. Electric polarization occurs when the microstructure of the configuration changes. The transverse flexoelectric coefficients μ12 of amorphous PVDF and PE configurations are 1.24×10-9 C/m and -2.63×10-9 C/m, respectively, obtained by fitting the relationship between polarization and strain gradient. Finally, through the micromechanical analysis, the CF2 and CH2 dipoles rotate around the main chain along the inner side of the curved surface under the strain gradient, accompanied by some small structural adjustments. This leads to the electric polarization of the amorphous PVDF and PE configuration. Due to the difference in charge number and electronegativity between the amorphous PVDF and PE groups, the calculated transverse flexoelectric coefficients of the amorphous PVDF and PE are opposite, and the absolute value of the transverse flexoelectric coefficient of PE is greater than that of PVDF.
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Affiliation(s)
- Taotao Hu
- School of Highway, Chang'an University, Xi'an, 710064, PR China; State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi'an Jiaotong University, Xi'an, 710049, Shaanxi, PR China.
| | - Lijun Chen
- School of Highway, Chang'an University, Xi'an, 710064, PR China
| | - Wei Mao
- Xinjiang Vocational and Technical College of Communications, Urumqi, 831401, PR China
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Allinger NL, Lii JH, Schaefer HF. Molecular Mechanics (MM4) Studies on Unusually Long Carbon-Carbon Bond Distances in Hydrocarbons. J Chem Theory Comput 2016; 12:2774-8. [PMID: 27164310 DOI: 10.1021/acs.jctc.5b00926] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The carbon-carbon single bond is of central importance in organic chemistry. When the molecular mechanics MM4 force field was developed beginning in the early 1990s, C-C bond lengths were not known very reliably for many important molecules, and bond lengths greater than 1.6 Å were quite poorly known experimentally. Quantum-mechanically computed values could not yet be obtained with useful accuracy in a general way. This paper examines structures now available from experiment and quantum-mechanical computations and extends the fit of the MM4 methodology to include new bond distances as long as 1.71 Å.
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Affiliation(s)
- Norman L Allinger
- Center for Computational Chemistry, University of Georgia , Athens, Georgia 30602, United States
| | - Jenn-Huei Lii
- CNC Gelcaps Corporation , No. 1205 Zhongzheng Road, Caotun Township, Nantou County 54254, Taiwan
| | - Henry F Schaefer
- Center for Computational Chemistry, University of Georgia , Athens, Georgia 30602, United States
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Chen KH, Lii JH, Fan Y, Allinger NL. Molecular mechanics (MM4) study of amines. J Comput Chem 2007; 28:2391-412. [PMID: 17486561 DOI: 10.1002/jcc.20737] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The MM4 force field has been extended to include aliphatic amines. About 20 amines have been examined to obtain a set of useful molecular mechanics parameters for this class. The vibrational spectra of seven amines (172 frequencies) calculated by MM4 have an overall rms error of 27 cm(-1), compared with corresponding MM4 value of 24 cm(-1) for alkanes. The rms and signed average errors of the moments of inertia of nine simple amines compared with the experimental data were 0.18% and -0.004%, respectively. The heats of formation of 30 amines were also studied. The MM4 weighted standard deviation is 0.41 kcal/mol, compared with experiment. Electronegativity effects occur in the hydrocarbon portion of an amine from the nitrogen, and are accounted for by including electronegativity induced changes in bond lengths and angles, and induced dipole-dipole interactions in the molecule. Negative hyperconjugation results from the presence of the lone pair of electrons on nitrogen, and leads to the Bohlmann bands in the infrared, and also to strong and unusual geometric changes in the molecules (Bohlmann effect), all of which are fairly well accounted for. The conformational energies in amines appear to be less straightforward than those for most other classes of molecules, apparently because of the Bohlmann effect, and these are probably not yet completely understood. In general, the agreement between the MM4 calculated results and the available data is reasonably good.
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Affiliation(s)
- Kuo-Hsiang Chen
- Department of Chemistry, Center for Computational Chemistry, Chemistry Annex, University of Georgia, Athens, Georgia 30605-2526, USA
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Chen KH, Lii JH, Walker GA, Xie Y, Schaefer HF, Allinger NL. Molecular Mechanics (MM4) Study of Fluorinated Hydrocarbons. J Phys Chem A 2006; 110:7202-27. [PMID: 16737272 DOI: 10.1021/jp060430x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A molecular mechanics study of small saturated hydrocarbons (up to C-6) substituted by up to six fluorines has been carried out with the MM4 force field. A parameter set has been developed for use in the calculation of bond lengths, bond angles, torsion angles, conformational energies, barriers to rotation, dipole moments, moments of inertia, and vibrational frequencies for these compounds. The results are mostly in fair to good agreement with experiment and ab initio calculations. The high electronegativity of fluorine leads to serious geometric consequences in these compounds, but these consequences can be dealt with adequately by suitable cross-terms in the force constant matrix, and by recognizing that some of the reference bond lengths and angles (l(0), theta(0)) and the corresponding stretching and bending constant parameters (k(s), k(theta)) that are usually thought of as constants must in fact be treated as functions of the electronegativity of the substituents. Additionally, the heavy mass of the fluorine (relative to the mass of hydrogen in alkanes) leads to large values for other cross-terms that were found to be unimportant in hydrocarbons. Conformational equilibria for polyfluorinated compounds are affected by the delta-two effect well-known in carbohydrates. A few larger fluorinated and polyfluorinated alkanes, including perfluoropropane, perfluorobutane, and Teflon, have also been studied.
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Affiliation(s)
- Kuo-Hsiang Chen
- Center for Computational Chemistry, Chemistry Annex, University of Georgia, Athens, 30602-2526, USA
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Makowska-Janusik M, Reis H, Papadopoulos MG, Economou IG, Zacharopoulos N. Molecular Dynamics Simulations of Electric Field Poled Nonlinear Optical Chromophores Incorporated in a Polymer Matrix. J Phys Chem B 2004. [DOI: 10.1021/jp036197+] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Allinger NL, Chen KH, Lii JH, Durkin KA. Alcohols, ethers, carbohydrates, and related compounds. I. The MM4 force field for simple compounds. J Comput Chem 2003; 24:1447-72. [PMID: 12868110 DOI: 10.1002/jcc.10268] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Simple alcohols and ethers have been studied with the MM4 force field. The structures of 13 molecules have been well fit using the MM4 force field. Moments of inertia have been fit with rms percentage errors as indicated: 18 moments for ethers, 0.28%; 21 moments for alcohols, 0.22%. Rotational barriers and conformational equilibria have also been examined, and the experimental and ab initio results are reproduced substantially better with MM4 than they were with MM3. Much of the improvement comes from the use of additional interaction terms in the force constant matrix, of which the torsion-bend and torsion-torsion are particularly important. Induced dipoles are included in the calculation, and dipole moments are reasonably well fit. It has been possible for the first time to fit conformational energetic data for both open chain and cyclic alcohols (e.g., propanol and cyclohexanol) with the same parameter set. For vibrational spectra, over a total of 82 frequencies, the rms error is 27 cm(-1), as opposed to 38 cm(-1) with MM3. Both the alpha and beta bond shortening resulting from the presence of the electronegative oxygen atom in the molecule are well reproduced. The electronegativity of the oxygen is sufficient that one must also include not only the alpha and beta electronegativity effects on bond lengths, but also on angle distortions, if structures are to be well reproduced. The heats of formation of 32 alcohols and ethers were fit overall to within experimental error (weighted standard deviation error 0.26 kcal/mol).
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Affiliation(s)
- Norman L Allinger
- Computational Center for Molecular Structure and Design, Department of Chemistry, Chemistry Annex, University of Georgia, Athens, Georgia 30602-2526, USA.
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Lii JH, Chen KH, Durkin KA, Allinger NL. Alcohols, ethers, carbohydrates, and related compounds. II. The anomeric effect. J Comput Chem 2003; 24:1473-89. [PMID: 12868111 DOI: 10.1002/jcc.10269] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The anomeric effect has been studied for a variety of compounds using the MM4 force field, and also using MP2/6-311++G(2d,2p) ab initio calculations and experimental data for reference purposes. Geometries and energies, including conformational, rotational barriers, and heats of formation were examined. Overall, the agreement of MM4 with the experimental and ab initio data is good, and significantly better than the agreement obtained with the MM3 force field. The anomeric effect is represented in MM4 by various explicit terms in the force constant matrix. The bond length changes are accounted for with torsion-stretch elements. The angle changes are accounted for with torsion-bend elements. The energies are taken into account with a number of torsional terms in the usual way. A torsion-torsion interaction is also of some importance. With all of these elements included in the calculation, the MM4 results now appear to be adequately accurate. The heats of formation were examined for a total of 12 anomeric compounds, and the experimental values were fit by MM4 with an RMS error of 0.42 kcal/mol.
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Affiliation(s)
- Jenn-Huei Lii
- Department of Chemistry, Computational Center for Molecular Structure and Design, Chemistry Annex, University of Georgia, Athens, Georgia 30602-2526, USA
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Yoshida T, Sakakibara K, Asami M, Chen KH, Lii JH, Allinger NL. Molecular mechanics (MM3) calculations on lithium amide compounds. J Comput Chem 2003; 24:319-27. [PMID: 12548723 DOI: 10.1002/jcc.10161] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The MM3 force field has been extended to deal with the lithium amide molecules that are widely used as efficient catalysts for stereoselective asymmetric synthesis. The MM3 force field parameters have been determined on the basis of the ab initio MP2/6-31G* and/or DFT (B3LYP/6-31G*, B3-PW91/6-31G*) geometry optimization calculations. To evaluate the electronic interactions specific to the lithium amides derived from the diamine molecules properly, the Lewis bonding potential term for the interaction between the lithium atom and the nonbonded adjacent electronegative atom such as nitrogen was introduced into the MM3 force field. The bond dipoles were evaluated correctly from the electronic charges on the atoms calculated by fitting to the electrostatic potential at points selected. The MM3 results on the molecular structures, conformational energies, and vibrational spectra show good agreement with those from the quantum mechanical calculations.
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Affiliation(s)
- Takashi Yoshida
- Department of Applied Chemistry, Yokohama National University, 79-5 Tokoiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
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Tang CY, Coxall RA, Downs AJ, Greene TM, Kettle L, Parsons S, Rankin DWH, Robertson HE, Turner AR. Molecular structure of trimethylphosphine–gallane, Me3P·GaH3: gas-phase electron diffraction, single-crystal X-ray diffraction, and quantum chemical studies. Dalton Trans 2003. [DOI: 10.1039/b306736j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lii JH. Molecular Mechanics (MM4) Studies of Carboxylic Acids, Esters, and Lactones. J Phys Chem A 2002. [DOI: 10.1021/jp0142029] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jenn-Huei Lii
- Computational Center for Molecular Structure and Design, Department of Chemistry, Chemistry Annex, The University of Georgia, Athens, Georgia 30602-2526
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Chen KH, Allinger NL. Molecular mechanics (MM4) study of saturated four-membered ring hydrocarbons. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(01)00760-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Affiliation(s)
- Kuo‐Hsiang Chen
- Computational Center for Molecular Structure and Design, Department of Chemistry, University of Georgia, Athens, Georgia 30605‐2556, USA
| | - Norman L. Allinger
- Computational Center for Molecular Structure and Design, Department of Chemistry, University of Georgia, Athens, Georgia 30605‐2556, USA
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Ivanov PM. Computational study on the ring distortions of 1,4-dicyanobenzene in the gas phase and in the crystal. J Mol Struct 1998. [DOI: 10.1016/s0022-2860(97)00263-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Mastryukov VS, Chen KH, Simonsen S, Allinger NL, Boggs JE. Ab initio and molecular mechanics studies of thianthrene and similar molecules. J Mol Struct 1997. [DOI: 10.1016/s0022-2860(97)00164-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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