The lithium abundances for 378 G/K giants are derived with non-LTE correction considered. Among these, there are 23 stars that host planetary systems. The lithium abundance is investigated, as a function of metallicity, effective temperature, and rotational velocity, as well as the impact of a giant planet on G/K giants. The results show that the lithium abundance is a function of metallicity and effective temperature. The lithium abundance has no correlation with rotational velocity at vsini < 10 km s −1 . Giants with planets present lower lithium abundance and slow rotational velocity (vsini < 4 km s −1 ). Our sample includes three Li-rich G/K giants, 36 Li-normal stars and 339 Li-depleted stars. The fraction of Li-rich stars in this sample agrees with the general rate of less than 1% in literature, and the stars that show normal amounts of Li are supposed to possess the same abundance at the current interstellar medium. For the Lidepleted giants, Li deficiency may have already taken place at the main sequence stage for many intermediate-mass (1.5-5 M ⊙ ) G/K giants. Finally, we present the lithium abundance and kinematic parameters for an enlarged sample of 565 giants using a compilation of literature, and confirm that the lithium abundance is a function of metallicity and effective temperature. With the enlarged sample, we investigate the differences between the lithium abundance in thin-/thick-disk giants, which indicate that the lithium abundance in thick-disk giants is more depleted than that in thin-disk giants.

Based on the analysis of high-resolution spectra with a high signal-to-noise ratio, we have determined the abundances of the α-elements O, Si, Ca and Ti, the iron peak elements V, Fe and Ni, and the heavy element Ba without the consideration of non-local thermodynamic equilibrium (NLTE) effect and the light neutron-rich elements Na, Mg and Al with an NLTE analysis for 63 nearby red clump giants. Fe abundances cover a logarithmic range between −0.60 and +0.35 relative to solar. All abundance ratios with respect to Fe are similar to those found in the Sun. Hyperfine structure (HFS) was taken into account when calculating V lines. The difference in abundances obtained with and without HFS can be as large as 0.5 dex.

We have obtained relatively high resolution spectra of Northern hemisphere K dwarfs. This is the first spectrometric project dedicated only to K dwarfs. Earlier studies have concentrated on more massive F and G dwarfs. However, these stars have already undergone evolutionary effects, unlike K dwarfs, which offer more accurate information about the evolution of the Solar neighbourhood. We have determined the LTE abundances of 14 elements for 42 stars with initial metallicity range covered by −1.52 < [Fe/H] < 0.48. We confirm the discrepancy in the abundances derived from neutral and ionized lines. The solution to this problem cannot just be the modification of initial physical parameters, but requires fundamental changes in the modeling of K dwarfs.