@article {1418,
	title = {Exchange-correlation energy in molecules: A variational quantum Monte Carlo study},
	journal = {Physical Review A},
	volume = {74},
	number = {3},
	year = {2006},
	note = {<p>ISI Document Delivery No.: 091ZPTimes Cited: 3Cited Reference Count: 48Cited References:      Cancio AC, 2006, PHYS REV B, V74     NEEDS RJ, 2004, CASINO VERSION 1 7 U     Gonze X, 2002, COMP MATER SCI, V25, P478, DOI 10.1016/S0927-0256(02)00325-7     LESTER WA, 2002, RECENT ADV QUANTUM 2     Cancio AC, 2001, PHYS REV B, V64, DOI 10.1103/PhysRevB.64.115112     Puzder A, 2001, PHYS REV A, V64     Nekovee M, 2001, PHYS REV LETT, V87, DOI 10.1103/PhysRevLett.87.036401     Foulkes WMC, 2001, REV MOD PHYS, V73, P33, DOI 10.1103/RevModPhys.73.33     PERDEW JP, 2001, AIP C P, V577     Proynov E, 2000, J CHEM PHYS, V113, P10013, DOI 10.1063/1.1321309     Perdew JP, 1999, PHYS REV LETT, V82, P5179, DOI 10.1103/PhysRevLett.82.5179     Kent PRC, 1999, PHYS REV B, V59, P12344, DOI 10.1103/PhysRevB.59.12344     KRIEGER JB, 1999, ELECT CORRELATIONS M     Van Voorhis T, 1998, J CHEM PHYS, V109, P400, DOI 10.1063/1.476577     Hood RQ, 1998, PHYS REV B, V57, P8972, DOI 10.1103/PhysRevB.57.8972     Fuchs M, 1998, PHYS REV B, V57, P2134, DOI 10.1103/PhysRevB.57.2134     Filatov M, 1998, PHYS REV A, V57, P189, DOI 10.1103/PhysRevA.57.189     Hood RQ, 1997, PHYS REV LETT, V78, P3350, DOI 10.1103/PhysRevLett.78.3350     Perdew JP, 1997, PHYS REV LETT, V78, P1396, DOI 10.1103/PhysRevLett.78.1396     LESTER WA, 1997, RECENT ADV QUANTUM M     Perdew JP, 1996, PHYS REV LETT, V77, P3865, DOI 10.1103/PhysRevLett.77.3865     Filippi C, 1996, J CHEM PHYS, V105, P213, DOI 10.1063/1.471865     GROSSMAN JC, 1995, PHYS REV LETT, V75, P3870, DOI 10.1103/PhysRevLett.75.3870     GROSSMAN JC, 1995, PHYS REV LETT, V74, P1323, DOI 10.1103/PhysRevLett.74.1323     UMRIGAR CJ, 1994, PHYS REV A, V50, P3827, DOI 10.1103/PhysRevA.50.3827     HAMMOND BL, 1994, MONTE CARLO METHODS     ENGEL E, 1993, PHYS REV B, V47, P13164, DOI 10.1103/PhysRevB.47.13164     GORLING A, 1993, PHYS REV B, V47, P13105, DOI 10.1103/PhysRevB.47.13105     GARCIA A, 1992, PHYS REV B, V46, P9829, DOI 10.1103/PhysRevB.46.9829     FAHY S, 1990, PHYS REV LETT, V65, P1478, DOI 10.1103/PhysRevLett.65.1478     SCHMIDT KE, 1990, J CHEM PHYS, V93, P4172, DOI 10.1063/1.458750     PARR RG, 1989, DENSITY FUNCTIONAL T, P186     BECKE AD, 1988, PHYS REV A, V38, P3098, DOI 10.1103/PhysRevA.38.3098     UMRIGAR CJ, 1988, PHYS REV LETT, V60, P1719, DOI 10.1103/PhysRevLett.60.1719     LEE CT, 1988, PHYS REV B, V37, P785, DOI 10.1103/PhysRevB.37.785     LEVY M, 1985, PHYS REV A, V32, P2010, DOI 10.1103/PhysRevA.32.2010     PERDEW JP, 1985, PHYS REV LETT, V55, P1665, DOI 10.1103/PhysRevLett.55.1665     HARRIS J, 1984, PHYS REV A, V29, P1648, DOI 10.1103/PhysRevA.29.1648     NORTHRUP JE, 1983, PHYS REV A, V28, P1945, DOI 10.1103/PhysRevA.28.1945     REYNOLDS PJ, 1982, J CHEM PHYS, V77, P5593, DOI 10.1063/1.443766     PERDEW JP, 1981, PHYS REV B, V23, P5048, DOI 10.1103/PhysRevB.23.5048     HAMANN DR, 1979, PHYS REV LETT, V43, P1494, DOI 10.1103/PhysRevLett.43.1494     ANDERSON JB, 1976, J CHEM PHYS, V65, P4121, DOI 10.1063/1.432868     GUNNARSSON O, 1976, PHYS REV B, V13, P4274, DOI 10.1103/PhysRevB.13.4274     VONBARTH U, 1972, J PHYS C SOLID STATE, V5, P1629     KOHN W, 1965, PHYS REV, V140, P1133     HOHENBERG P, 1964, PHYS REV B, V136, pB864, DOI 10.1103/PhysRev.136.B864     KATO T, 1957, COMMUN PUR APPL MATH, V10, P151, DOI 10.1002/cpa.3160100201Hsing, C. R. Chou, M. Y. Lee, T. K.AMERICAN PHYSICAL SOCCOLLEGE PK</p>
},
	month = {Sep},
	pages = {10},
	type = {Article},
	abstract = {<p>We have used the combination of the coupling-constant integration procedure and the variational quantum Monte Carlo method to study the exchange-correlation (XC) interaction in small molecules: Si-2, C2H2, C2H4, and C2H6. In this paper we report the calculated XC energy density, a central quantity in density functional theory, as deduced from the interaction between the electron and its XC hole integrated over the interaction strength. Comparing these "exact" XC energy densities with results using the local-density approximation (LDA), one can analyze the errors in this widely used approximation. Since the XC energy is an integrated quantity, error cancellation among the XC energy density in different regions is possible. Indeed we find a general error cancellation between the high-density and low-density regions. Moreover, the error distribution of the exchange contribution is out of phase with the error distribution of the correlation contribution. Similar to what is found for bulk silicon and an isolated silicon atom, the spatial variation of the errors of the LDA XC energy density in these molecules largely follows the sign and shape of the Laplacian of the electron density. Some noticeable deviations are found in Si-2 in which the Laplacian peaks between the atoms, while the LDA error peaks in the regions "behind" atoms where a good portion of the charge density originates from an occupied 1 sigma(u) antibonding orbital. Our results indicate that, although the functional form could be quite complex, an XC energy functional containing the Laplacian of the energy is a promising possibility for improving LDA.</p>
},
	keywords = {ATOMS, DENSITY, EXPANSION, FUNCTIONALS, GENERALIZED GRADIENT APPROXIMATIONS, POTENTIALS, Silicon, SOLIDS, SYSTEMS, WAVE-FUNCTIONS},
	isbn = {1050-2947},
	url = {<Go to ISI>://WOS:000241067100069},
	author = {Hsing, C. R. and Chou, M. Y. and Lee, T. K.}
}
