2008 3 Mar. 2008 CHEMICAL INDUSTRY AND ENGINEERING 25 2 Vol. 25 No. 2 :1004-9533 (2008) 02-0160 - 06,, (, 300072) : (MD),,,,,, 5 % : ;;; ; :O645116 :A Molecular Dynamics Simulation of High Temperature and Pressure Water DONG Yan2ping, DONG Xiu2qin, ZHANG Min2hua ( Key Laboratory for Green Chemical Technology, Ministry of Education, Tianjin University, Tianjin 300072, China) Abstract :Microscopic structure, hydrogen2bond and self2diffusion properties of high temperature and pressure water were investigated by using molecular dynamics (MD) simulation. Moreover, the average geometrical configuration of water molecules at different state were analyzed. It was found that, with increasing temperature, the average number of hydrogen bond in water decreased, and the average geometrical configuration of water molecules changed regularly, bond length became shorter and H O H angle became larger. The changes were remarkable around the supercritical point. The microscopic structures of sub2critical and super2critical water were different from that of ambient water. The calculated self2diffusion coefficients of water agreed well with the experimental ones within less than 5 percent relative error. Key words :molecular dynamic (MD) simulation ; super2critical water ; microscopic structure ; hydrogen bond ; diffusion coefficient,(scw) [1 4],,, Kalinichev [5] BJ H SCW Nieto2Draghi [6] TIP4P SPCΠE TIP5P DEC4 COMPASS ( Condensed2phase Optimized Molecular Potentials for Atomistic Simulation Studies) [7], :2006-11 - 28 : (1982 - ),,, :, : (022) 27406119,E2mail :xqdong @tju. edu. cn
25 2 : 161 015 fs (1 fs = 10-15 s), MD,, COMPASS [8,9] 300 ps, 100 ps 1 MD MD [10 ],,,,, 2 MD 256,, (ab initio) COMPASS,, Maxwell2Boltzmann Group based, Velocity2Verlet [11 ] NVT, [12 ],, 200 ps NVE, 200, 3,, Group based [9 ] Ewald [13 ], 1 2 Πnm 1 Π( ) Πcm - 1 Πcm - 1 Πcm - 1 MD 01957 104152 3 657 3 755 1 594 2 01957 2 [14 ] 104152 [14 ] 3 657 [15 ] 3 756 [15 ] 1 595 [15 ] Π D MD D Exp. TΠK Π(g cm - 3 ) h 10 9 Π(m 2 s - 1 ) 10 9 Π(m 2 s - 1 ) % 29812 01997 Group based 410 2124 Ewald 5512 2144 213 [16 ] - 2161 6109 67312 01251 Group based 219 122154 Ewald 5016 124102 125 6 [17 ] - 1197-0178 67312 01170 Group based 1155 187170 Ewald 3712 174195 191 10 [17 ] - 1173-8140 773 01217 Group based 2175 169109 Ewald 4315 173103 162 [18 ] 4138 6181 1, 2, Group based, 5 %,, Group based Ewald, Ewald Group based, (vdw) (Coulomb)
162 2008 3 Group based 311, (Ridial distribution function, RDF) r : g ( r) = ( r) : ( r) r ; (4) 1 4 O O H, 25 MPa ; TΠK: - - - 57312 ; 2222 62312 ; 65312 1 57312 65312 K O H 25 MPa, TΠK: - - - 68312 ; 72312 ; 76312 2 68312 76312 K O H 25 MPa, TΠK: - - - 57312 ; 222 62312 ; 65312 3 57312 65312 K O O 25 MPa 57312 65312 K g OH ( r) 01185 nm 01345 nm ( 1) ; 25 MPa 68312 76312 K g OH ( r) 01195 nm,01205 nm,01215 nm, 25 MPa, TΠK: - - - 68312 ; 222 72312 ; 76312 4 68312 76312 K O O 01345 nm ( 2),,,O H,, 1 2, 2 g OH ( r)
25 2 : 163 1,, ( T c = 64712 K) ( P c = 2118 MPa), 68213 K 72312 K, g OH ( r), 76312 K,,, ;, 3 4,,, g oo ( r),,,, 312, [19 ], O H r OH 0124 nm, O O H < 30 ( 5 ) n HB 3 5 3124, Gu rdia [20 ] 3,,,,,,,,,,,,,,, 3 Π nm Π ( ) 29812 K,011 MPa 3124 01097 63 99145 57312 K,25 MPa 1173 01097 396 100158 62312 K,25 MPa 1147 01097 316 100196 65312 K,25 MPa 1113 01097 157 101150 68312 K,25 MPa 0153 01096 818 102184 72312 K,25 MPa 0142 01096 769 103115 76312 K,25 MPa 0133 01096 748 103140 68312 K,300 kgπm 3 0189 01097 017 101199 72312 K,300 kgπm 3 0184 01097 032 102109 76312 K,300 kgπm 3 0181 01097 057 102115 80312 K,300 kgπm 3 0176 01097 077 102128 313 : Green2 Kubo Einstein Einstein [21 ], D self D self N 1 = lim t 6 Nt r i ( t) - r i (0) 2 (5) i = 1,r i ( t),, 1Π6, 6 7 pπmpa : 23 ; 25 ; 27 ; 29 6
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