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首页> 外文期刊>Physical review >Correlation energy within exact-exchange adiabatic connection fluctuation-dissipation theory: Systematic development and simple approximations
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Correlation energy within exact-exchange adiabatic connection fluctuation-dissipation theory: Systematic development and simple approximations

机译：精确交换绝热连接波动耗散理论中的相关能量：系统发展和简单近似

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We have calculated the correlation energy of the homogeneous electron gas (HEG) and the dissociation energy curves of molecules with covalent bonds from an efficient implementation of the adiabatic connection fluctuation dissipation expression including the exact-exchange (EXX) kernel. The EXX kernel is defined from first-order perturbation theory and used in the Dyson equation of time-dependent density-functional theory. Within this approximation (RPAx), the correlation energies of the HEG are significantly improved with respect to the random phase approximation (RPA) up to densities of the order of r_s ≈ 10. However, beyond this value, the RPAx response function exhibits an unphysical divergence and the approximation breaks down. Total energies of molecules at equilibrium are also highly accurate, but we find a similar instability at stretched geometries. Staying within an exact first-order approximation to the response function, we use an alternative resummation of the higher-order terms. This slight redefinition of RPAx fixes the instability in total energy calculations without compromising the overall accuracy of the approach.
机译：我们已经从包括精确交换（EXX）内核的绝热连接波动耗散表达式的有效实现中计算出了均质电子气（HEG）的相关能和具有共价键的分子的离解能曲线。 EXX内核是根据一阶微扰理论定义的，并用于依赖时间的密度泛函理论的戴森方程中。在此近似值（RPAx）内，相对于随机相位近似（RPA），HEG的相关能得到了显着改善，密度达到r_s≈10的量级。但是，超过该值，RPAx响应函数表现出不物理的散度和近似分解。处于平衡状态的分子的总能量也非常精确，但是我们发现在拉伸的几何结构中存在类似的不稳定性。为了保持响应函数的精确一阶近似，我们使用了另一种高阶项的求和。 RPAx的这种轻微重新定义解决了总能量计算中的不稳定性，而不会影响该方法的整体准确性。

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